I don't think this is as clear cut as people on both sides of the debate seem to think. 

We do have freedom of association, but then we have had to legislate equal rights for minorities. Should homosexuals be part of a protected class? I don't know. 

What I do know reasonably well is what the Bible has to say. Although it makes clear that homosexuality is a sin, it also says very clearly not to judge and to love your neighbor. It says nothing about selling a cake to a gay couple, not even in the message version. Selling a cake is just commerce and if I were the baker, I would not have refused. I would have simply made the best cake I could make. Heck, if he wanted to do so, he could have given them a free bible with the purchase. 

Again, I don't know if he should be legally able to refuse to bake the cake, I just don't think Christ would require it.