Temptation and thoughts are certainly not an inherent sin, but the consensus remains among most church bodies that being openly homosexual and engaging in the actions is a sin and by refusing to repent you repeatedly deny God. The catholic and evangelical churches continue to support traditional beliefs, while mainline protestant churches support it. Interestingly enough, evangelical churches are growing and mainline churches are shrinking.
Two Questions:
1. Can you be a "gay" christian?
2. Are mainline churches' progressive stances turning away members?
Sex is only not a sin when it happens between a man and a woman who are married to each other and it is there first marriage unless their previous partner has died.
People who choose to lead a sexual lifestyle outside of that parameter are not followers of Christ. People who trangress through weakness and acknowledge that what they have done is wrong and ask for forgiveness can be followers of Christ.