Read the link — then, laugh at the silly nature of the whole darned thing.
Talk about how NOT to make good arguments — right there… maybe, just maybe, there ARE no good arguments against same sex marriage. If you aren’t gay, don’t marry a gay person. If your religion has told you it’s wrong to do, don’t do it. Just don’t expect that other people will think the same thing — they don’t agree with you on other stuff (favorite ice cream flavors etc..) and you don’t try to force that on them — why something much more basic and intrinsic to human happiness like who you love?