I assume that you were presenting ‘their’ argument, but, just to be sure, the counter argument to what you posited is that race is something that is beyond a person's control to change (except if you have Michael Jackson's wealth) while sexuality is a preference. This is why the homonfascists changed the term from “sexual preference” to “sexual orientation” — it makes it sound more like a condition from birth.
As the argument against gay marriage is, “where does it end, should parents and children or two brothers or two sisters be able to marry? Or is polygamy acceptable, then?” so the argument against homosexuality as an unalterable condition and therefore deserving of “human rights” protections would be that of heterosexual, serial adultery. That is, if homosexuals can claim their behavior should be protected, then heterosexual men who are married can claim to have a condition that forces the to commit adultery and they should therefore be a protected class.
This is absurd, of course, as both are behavioral choices. But this is where the homofascists have led this country with their accomplices in black robes.
In the school's statement on the matter, clearly, the issue here is the student's conduct. That is, he has been suspended because he participated actively in pornography. It doesn't matter what type of pornography.
Of course, his lawyer might try to twist the story to make it look like an issue of sexual orientation. If so, can't a private college that doesn't accept government funds refuse to accept a student on any basis? It's my understanding that Grove City is a private college that refuses government funds so that they don't have to abide by Title IX. (I also read the school has a thriving women's sports program without Title IX.)
This is an open and shut case. The school was well within its rights. I doubt even the most liberal activist group will file a case (since they know it will be thrown out. There are dozens of test cases which show that a private school can indeed demand moral conduct of its students. A Christian college is in no way forced to accept Satanists, sodomites, or NAMBLA members. Luckily, religious groups still have a few freedoms left. This sick kid had no business working in homo-porn (think of the AIDS danger alone). He should have just gotten a regular job instead of seeking quick cash.