What if he did? I wouldn't agree with him about it, but we either have liberty of thought and belief and the right to be who we are and practice our convictions so long as we are not infringing on anybody else's right to the same or we do not. It is WRONG to have protected classes for some people and not everybody in that regard. It isn't a matter of what constitutes the law in that regard. It is a matter of liberty and right and wrong. The law interpreted that somebody has to participate in an event that violates his religious views, his principles, his convictions is a very, very bad law.
A gay person should always be able to be who he or she is in peace, without harassment, and without expectation that he must agree with and/or accommodate an event with which he has a moral, philosophical, or ethical problem with. And so should the gay or heterosexual Christian. It is as simple as that.