Marriage is so gay, should I get one?

[colinmackay]

Er.... isn't GAY a straight word meaning BAAAAAAD ????? I don't know if I'd want to wear a t-shirt that meant something so ambiguous.

I think that's the point. It is used as a way to campaign for Gay Marriage equality by making an ironic statement about the institution of marriage by using a word that can also have a negative connotation in a certain idiomatic contexts, e.g. the expression "<noun/verb> is so gay!"

Essentially, the statement is an insult to marriage, just as lack of equality for marriage for gay couples is an insult to us.