Um, yeah. It's used as an excuse. Even if you consider homosexuality to be a sin, we all sin. So why fight over only one type of sin within a congregation rather than loving them and welcoming them, just as we love and welcome other sinners (including ourselves)?
Homosexuality isn't what is divisive- it is forgetting that Jesus sat with, ate with, loved, and saved sinners. If we are to be Christ-like, then we are to focus on our own issues while offering our service (not our condemnation) to others.This is why more and more people are leaving Christianity. The actions of congregants are not aligned with the actions and teachings of Christ. Christ taught forgiveness, love, healing, and sharing. Just as in Jesus' day he was seen as threatening in his liberality toward all people, those people who seek to emulate him today are also often seen as too liberal.