Do I believe a Christian can sin, and even live in sin for a time? Yes. Do I believe that a Christian can be disobedient to God? Of course. But I would say that homosexual relations are an abomination to God. And in the long run, you will know people by the fruit of their lives. If one lives in the sin of homosexual behavior, heterosexual adultery, lust, gossip, drunkenness, etc., I believe their life is showing by the fruits that their profession of faith in Christ is likely not genuine, and therefore they are not saved. But only God can know that for sure.