I disagree with the idea that the left somehow has a lock on condescending or "holier-than-thou" attitudes.  Two examples from the right, the knee-jerk reaction that anyone who questions going to war, or our commander-in-chief's motives, must be unpatriotic, terrorist appeasers, and should love our country or leave it; and the biggie, from the christian right, anyone who disagrees with them is doomed to burn in hell for eternity.

There are obnoxious blowhards of all ideologies, and political persuasions.

If someone debates the pros and cons of an issue, explains a point of of view, either politely, or uses sarcasm, satire, or colorful language (Kravitz!),  I'll listen, and might even change my mind, but start a discussion with an attack or stereotypical accusation and I'll ignore everything else a person has to say.