Hello Eddie,
I am by no means an expert in theology, but here is my opinion. If
someone has "lapses" in their behaviour and finds themselves going back
to homosexual acts, I would say that that sin would be regarded as any
sin. Something that the person would feel guilty about commiting. The
problem I have with homosexual marriage is that the person would be
trying to legitimize homosexuality. He would be denying that it is a sin
and expecting God to be okay with it. In this case I would have to
question if that individual was genuinely saved. Because the Holy Spirit
convicts us of all sin, I don't think a true christian could or would
choose to live against God's will purposely. Just my 2 cents :)
Jeff