If you've spent any time around the tubes, especially if you've spent any time on social media sites, particularly digg, you've encountered them. They're often young, brash, obnoxious, overly confident(, Linux users)* -- until you cut their baseless arguments to shreds or otherwise disprove their irrational case. They're wikidemics.
*Disclaimer: I run two different distros at home. I'm just saying.