I don't know about Judaism, but homosexuality is not something that is explicity banned in Christianity. Yeah there are some bible passages against it, but there are also bible passages condoning slavery, polygamy, forced marriage etc. If one were to be a strict adherent to the bible one would have to take some far-out stances on some issues.

Truth is that just because there are some parts of a religion that may support discrimination or other negative behavior, doesn't mean followers of that religion have to agree with that. Many people ignore the parts they don't agree with.