No. Of course not.
While I also don’t buy the whole “you can’t help who you’re attracted to” bit (because you can), I don’t think an orientation is a sin (nor am I willing at this point to accept that there is such a thing as an orientation). A sin is not a state of being. A sin is an act.
Taking this away from the homosexual aspect, let’s have an example.
I’m married to Stan. I meet Gary. Gary is hot. Whoo boy.
At this point, I can – yes, I can – choose whether or not to be attracted to Gary. Honestly, I can. I can acknowledge that I think Gary is hot, recognize this as a potential problem, and take steps to mitigate it. I can consciously turn my thoughts from Gary and to Stan. I can.
I can also choose whether to act on the attraction I have to Gary. I can choose to have sex with him, or I can choose to remain faithful to my husband. Just because I think Gary is a hottie doesn’t mean I have to do it with him.
Being attracted to someone is not (necessarily) a sin. How you choose to react to that attraction could be a sin.
My personal theory is that everyone has a cross to bear, you know? Everyone has SOMETHING that’s continually pulling them down a wrong path. Shopping, eating, being lazy, a love of alcohol. Whatever. For some people, that “something” is sexual feelings, or who they are attracted to. But we are not animals and we are not slaves to our instincts. Just because I hear that beer calling my name from across the room doesn’t mean I have to go drink it.
And that’s my short, I’ve had a long day thesis on that. I’m probably done discussing this. If you want to read more on my thoughts about the Bible, etc., you’ll have to satisfy yourself with clicking on the “christianity” category to the right.