Anti-discrimination laws do not just protect people for traits "they
are born into." If that were the case, there would be no protection for
the free exercise of religion, speech, or political opinion.
Quite untrue, I'm afraid. While you have the right to say whatever you want, you don't have the right to not be affected negatively by what you say. A man who decides to say "I hate niggars and kikes." in a bar downtown, would likely be fired from his job should his employer find out about it. And noone would think twice about siding with the employer if he sued. However, 60 years ago, the same thing cannot be said.
As for exercising religious freedoms, people will still be brought to court for animal cruelty for sacrificing an animal in the name of their religion. Granted, most get off, but it still happens. Not to mention the present (and continuing) discrimination (and prosecution) against Mormons for their belief in Polygamy.
It all depends on what the majority of people in an area believe. People may not like it, but that is the way America works. And right now, people believe that homosexuality is a choice. And it's not something that deems the legal term of marriage for. It may be wrong, and people may not like it. But if homosexuals feel so angry, perhaps they'll march across America from San Fransisco to DC like others who have had their rights kept from them.
But, even if such a thing were to happen, until homosexuality is pervasively viewed as not a choice, but something people are born into, the RIGHT to marry, will likely not be given across the board.
African Americans dealt with separate but equal for 20 years. Angrily, but they did. It seems that homosexuals will have to do the same. For how long, though, is up to them.