"If you think X, you clearly don't understand Y at all!"
Ever hear that? "You're stupid because you don't know how brilliant this liberal whatever!" Usually it is accompanied by either a quote about how much more they know than you (or the person they are quoting), or how much more educated they (or the person they are quoting) is, or how you're just plain dumb for believing whatever it is you believe.
It's a common debating tactic amongst liberals. Most of the time, they excuse it as "no, your points really are stupid so my condescension is validated." (I pretty much guarantee I'm going to get at least one of these via tweet or comment.) Liberals love to talk down to everyone. They're smarter than everyone, just ask them!
Often, this condescension is used in replacement of an actual argument. I spoke recently with an individual who was arguing with me for the need for hate-crime legislation. Ultimately, when I responded to all of his arguments, I was told he knew what he was talking about more than me because he went to law school. There was no need for him to provide actual evidence of the necessity of such laws when...you know...actions like murder and assault are illegal, regardless of the motive behind the crime. He knew better because he was a self-described expert. (By the way, to this day, I have no idea if this individual's legal expertise was in criminal law, real estate, or business mergers.)
Yet another condescender was a person who I've known for years. This individual always feel back on the typical liberal response of "LOL, that's stupid because reasons." When asked for evidence, I would further be told how I should accept what Expert X said, again, because reasons. (Please note that "because reasons" doesn't equal actual evidence, just a one-off bumper sticker quote.) These arguments fall in the same category with the classic statement "Italians are never wrong, just ask one!"
Far too many Activist Liberals use this tactic as a shut-down. It's all about making you feel like you don't even deserve to debate with them. Ultimately, the answer is to walk away from these individuals. At Biblical Conservatism, repeated condescension will get you blocked as a commenter, both here at the blog and on our Facebook Page. In real life, it generally is best to just walk away. If someone won't debate with respect, it's not worth debating with them. Let them look like a jerk, then walk away.