1. Illogical means that there's no logic. There definitely is a logical reason, I named just one of those reasons, another is simply that it is their belief system, something that you're in compliance with simply by attending the school.
2. We've been through this several times, and we've established you're intolerant of their religious views. However, your opinion really doesn't cut it in this argument when you're putting it above the opinions of others.
As for your other point, that's incorrect, the rules are justified. It's not a high school, it's a religious, private institution, where they're allowed to have their own regulations, as long as they cooperate with the laws of the United States. Your comparison is just silly and irrational.
3. They have their own principles, we have ours. He agreed to the rules, that's really all there is to it.
4. Logical fallacy, you implied that BYU condones polygamy, which I will repeat again, is prohibited by the Book of Mormon. You're really starting to backpedal.