It was a pun on a pejorative use of the word - if you disagree, look up "pejorative".
At the risk of seeming "PC" to oversensitive folks, using social identities as pejoratives is inherently insulting; you're associating their racial/sexual/etc. identity with something undesirable, even if you don't think of it as a slur. "Gay" to mean stupid or annoying is of a piece with terms like "gyp", "indian-giver", or "nigger-rig".