I wrote this about the Church, then realized you were specifically addressing BYU. Whoops. I added in some stuff to address that, but apologies if I'm too focused on the Church and not BYU!
I wrote up a long response on why I agreed with you, but not for the reasons you stated. Instead, I thought the Church would respond differently due to the extent to which gospel teachings interact with these two different groups. I argued (in error) that LGBTQ+ issues were more wrapped up in Church teachings (Family Proclamation, gender roles, eternal destiny of men and women, who holds the priesthood in the home, how to create spirit children and worlds if it's just two men/women) than the priesthood and temple ban for African Americans and Africans (racism in scriptures, view of the pre-existence and who was/wasn't valiant, justifications for why some are born into the gospel/wealth).
But then I thought about it more. And I realized we've changed so much in our history that the only doctrine that cannot change is that the prophet receives continuing revelation and can make changes to doctrine/practice. Thus, it doesn't matter to what extent Church teachings (about blacks, about the pre-existence, about gender roles, about family) intersect with these groups. (Which, by the way, the temple and priesthood ban was a bigger part of the doctrine back then; I was making a racist assumption that it wasn't that big a deal when instead I needed to recognize that we've been downplaying it, the doctrine around it, and the absolutely horrid things that blacks faced.) All of that can change the moment the prophet says he's received a revelation saying it must change. That a man must marry at least two wives was taught as fundamental to our eternal salvation (The First Presidency and Quorum of the Twelve Apostles wrote to U.S. President Benjamin Harrison, "We formerly taught to our people that polygamy or celestial marriage as commanded by God through Joseph Smith was right, that it was a necessity to man's highest exaltation in the life to come."), but that went away the moment the prophet said it did. Being black was a sign of God's disfavor and punishment until the prophet said it wasn't. It doesn't matter how entwined the doctrine is or isn't, or how crucial some may believe it is to our eternal salvation, because the moment the prophet says it must change, then so it will.
So ultimately I believe they are similar enough to each other to allow us to hypothesize how the Church (and BYU) will respond to them - they will change. It may take decades and we'll definitely get another offshoot, but it will change.
I do think you bring up some good points about why they may not be similar, so I wanted to address those points:
1. There wasn't scriptural justification for racism
The bible was used to justify racism. Please read those articles I linked, because it's really important that we all understand how people have used religious texts to justify discrimination and awful actions such as slavery, because it is crucial we understand our past to ensure a better future. And this applied to the LDS Church. According to Wikipedia,
the church taught that the ban came from God and officially gave several race-based explanations for the ban, including a curse on Cain and his descendants, Ham's marriage to Egyptus, a curse on the descendants of Canaan, and that black people were less valiant in their pre-mortal life. They used LDS scriptures to justify their explanations, including the Book of Abraham which teaches that the descendants of Canaan were black and Pharaoh could not have the priesthood because he was a descendant of Canaan.
We saw an example of scriptural justification for racism just recently. In 2 Nephi 5:21-22, we read
And he had caused the cursing to come upon them, yea, even a sore cursing, because of their iniquity. For behold, they had hardened their hearts against him, that they had become like unto a flint; wherefore, as they were white, and exceedingly fair and delightsome, that they might not be enticing unto my people the Lord God did cause a skin of blackness to come upon them. And thus saith the Lord God: I will cause that they shall be loathsome unto thy people, save they shall repent of their iniquities.
In a recent Church mini-scandal, someone discovered the printed Come, Follow Me manual had this quote by Joseph Fielding Smith on that scripture: "The dark skin was placed upon the Lamanites so that they could be distinguished from the Nephites and to keep the two peoples from mixing. The dark skin was the sign of the curse. The curse was the withdrawal of the Spirit of the Lord. ... Dark skin ... is no longer to be considered a sign of the curse." It sounds like Joseph Fielding Smith was just quoting the scriptures, so why would this cause a scandal? Please read the article I linked to, as it explains why this is a racist teaching. Many past prophets used scriptures similar to this to justify racism and slavery, as dark skin was a sign of a curse, made people loathsome and not enticing, and called for segregation and a ban on interracial marriages.
2. Race is non-behavioral, while homosexuality is behavioral
To be clear, the behavior you're talking about it acting on love for another and a desire to be loved. To argue homosexual behavior is just sexual is to argue that all heterosexual marriages are entered into only because the man and woman want to have sex and nothing else. Homosexuality is about wanting to make a human connection and, hopefully, have a lifelong marriage and partnership with another human who is equally attracted and devoted to you.
You argued that "As long as a homosexual member of the Church (or member of the BYU faculty) chooses to not act on their sexual proclivities, they can remain in good standing." But so could black members. Blacks were never not permitted to join the Church or not be members in good standing. Yet despite the fact that we can have faithful black and LGBTQ+ members, here's what both these members in good faith face(d):
- can't be sealed to those they love
- can't hold positions of authority (need the priesthood or a heterosexual marriage to be bishop or higher)
- face extreme racism or homophobia
- are told their innate characteristic will be changed in the next life (more)
- are told they won't be with those they love in the next life (more)
- face higher levels of suspicion and scrutiny (mostly applies to BYU)
- were told their problematic characteristic was their fault (being gay is a choice; not valiant in pre-existence)
Yes, there are definitely differences in the discrimination they faced, but it's crucial we recognize that, even though race is non-behavioral and homosexuality is behavioral, members in good standing in both groups still face discrimination. The only way for gays and lesbians to be treated as true, faithful members in good standing where they receive all the blessings and opportunities of heterosexual members is for them to enter into a mixed orientation marriage, where they face higher levels of depression, suicide, and divorce, where even famous Church members couldn't do it (please read the last linked article; it's a blog post from Josh Weed announcing his divorce). It makes sense that people in these marriages would face such pain, because as you pointed out, "Race and sexual orientation are both innate, intransigent characteristics."
Finally, we need to recognize the distinction between not acting on a normal behavior ("I love chocolate but to be healthy I'm not going to eat it anymore") and not acting on a fundamental human behavior ("I want to find love and acceptance but I can't or I'm sinning."). As Josh Weed wrote,
... I began to realize that there was actual science around this issue, and that that science actually made the statistical difference between gay people beginning to live a healthy life, and gay people exhibiting symptoms that, if not treated, would go from severe chronic depression/anxiety to psychosomatic illness to, eventually, death. For me, though, it all came down to the people I met with–the actual human beings who were coming to my office. They would come and sit down with me, and they would tell me their stories. These were good people, former pastors, youth leaders, relief society presidents, missionaries, bishops, Elder’s Quorum presidents, and they were . . . there’s no other way to say this. They were dying. They were dying before my eyes. And they would weep in desperation—after years, decades, of trying to do just as they had been instructed: be obedient, live in faith, have hope. They would weep with me, and ask where the Lord was. They would sob. They would wonder where joy was. As a practitioner, it became increasingly obvious: the way the church handled this issue was not just inconvenient. It didn’t make things hard for LGBTQIA people. It became more and more clear to me that it was actually hurting them. It was killing them.
Yes, LGBTQ+ individuals can decide to be celibate. But we shouldn't close our eyes to what it does to them.
Because the scriptures have been and are used to justify racism and homophobia, because homosexuality isn't just a behavior that can be switched off without causing harm, and because even faithful, celibate LGBTQ+ Church members are discriminated against, there is a clear parallel between BYU and the Church's discrimination against blacks and homosexuals.
-guppy of doom