That line about if you're not a liberal at 20, you have no heart, and if you're not a conservative at 30, you have no brain.
Mostly because I only hear it from smug Fox News viewers.
I loathe with a perfect passion the saying "God made Adam and Eve, not Adam and Steve". For similar reasons I dislike "They call it global warming, but it's God's Warning".
Oh, and people's obsession with slapping -gate onto everything remotely controversial makes me slightly murderous.