Why Are Liberals So Rude?

This is spot on. Leftists (I don’t call them “liberals”) assume that everyone with a brain or a conscience must share their opinions, which they never bother to defend rationally and probably couldn’t if they had to. The merest hint that you are not in lock-step with their world view (about which they rarely shut up) is taken as a license to sneer, roll eyes, and exclaim “well I just won’t bother with people who can’t accept the obvious.” (This over AGW. That’s verbatim. The woman, who was a guest, is a journalist and published author, and I’m pretty sure she couldn’t spell CO2.) I have been outright shouted down by two grown men, one a tenured University professor, for daring to suggest that Barack Obama wasn’t great presidential material – but only after they had baited me into a “conversation” I was not remotely interested in having, since I don’t go out of my way to pick fights, especially with people I know socially.

It never occurs to them that you might resent these egregious displays of bad manners. After all, it is a truth universally acknowledged that they are allowed to speak, and you are not allowed to speak. So you have it coming. It’s the price you pay for being a fascist. 
h/t Weasel Zippers