I've heard both sides of the issue.
The Anti Gay Marriage side says that being gay is immoral and that gay sex serves no purpose. Since normal sex can be used to have children, gay sex is based completely off of lust (one of the five evils) and has no biological purpose. I have also heard some people say that being gay is against Waheguru's will.
The Pro Gay Marriage side says that we should be accepting of everyone.
I just want to see what more learned people on this site think.