Well, the Bible says multiple times that homosexuality is a serious sin and comes from the devil. Just look at Sodom and Gomorrah, they were notorious for being gay and God destroyed them off the face of the planet. Homosexuality is condemned in the law of Moses and repeatedly discouraged and frowned upon by Paul. It goes against the order of creation, the one first demonstrated by Adam and Eve. Homosexual couples can't obtain what heterosexual couples can; at least, not without scientific aid.
I believe that Christian baker did what was right, because he absolutely could not, in good conscience, promote a belief that was against what he believed. I think every Christan should be like that.