What I define a sin as is anything that causes a person to stray from God's will. For the record, no one sin is greater than another.
I tried to keep my mouth shut, but this line got me. I think what bothers me most, is how can anyone pretend to know what the will of "God" is? Much less judge others and tell them they are wrong, simply because some book written thousands of years ago re-written a million times says so. Has anyone ever heard their "god" say homosexuality is wrong? I very seriously doubt it. Is it the same belief system that says when priests mollest children it's pardonable because they ask "god" for forgiveness?
So gay marriage is wrong because "god" says so, I'm sorry thats the same excuse some serial killers use. That mentallity is the same mentallity that causes people to strap bombs to themselves and kill innocents. This is my whole beef with organized religion. This is why my religious friends still refer to me as atheist when I repeatedly tell them that I believe in a creator just not you Christian god.
You want to be Christian and celebrate your religion go for it. But don't push it on those who don't follow, and don't pretend Christianity has a lockhold on the definition of marriage, marriage has been around a hell of a lot longer then Christianity it's not like your religion has a patent on it. If two people love one another and feel deeply enough to make a lifelong commitment, I think thats great.