Man, I hate the phrase "Don't Drink the Kool-Aid." It's the most thoughtless way to criticize someone for being thoughtless. If you lob this insult, you're essentially telling someone they're embracing the perspective of a particular group to the point that they've stopped thinking for themselves. But it's the most vitriolic, bumper-sticker way to say it. It's so abbreviated and self-righteous, there's no possible way to argue back against it. It's one of those arguments that someone makes to stop conversation, under the guise that they're actually making a good point.
Can we please respect people we disagree with a little bit? Just because someone has a different ideology, doesn't mean they would just blindly follow some thought leader into mass suicide.
FYI: If you're interested, a little on the entymology of the phrase, here, and here.