Anti-conservative

An anti-conservative is someone who defines his political positions to be against whatever the conservative position is.

Sometimes the logic is simply a matter of disliking someone or an institution perceived to be conservative and then adopting views that are the opposite of other disliked person. For example, "the ______ church holds this position, so I'm against it!" Or, to take another example, "my [father/mother/ex-husband/ex-wife] thinks such-and-such, so I'm against that!"

Note that these individuals display no intellectual rigor. They hold no positions of their own, merely gainsaying anything said by the opposing party.