In practice, the rule came to be in response a few years back to a decided upswing in pejoratives such as "Republicunt," "Democrap," or "Libertard," along with similar "witty" nicknames for prominent members of those parties ("Mittens," "Obummer", etc.) The main goal was to cut down that sort of snarking that served absolutely no purpose save for to degrade and rile up people. Some comments are less crystal-clear, and would need to be looked at case-by-case in the full context of the conversation to make that determination.
The rule is mainly meant to deter the absurdly blatant non-debating garbage like the examples I've given, and technically falls under the umbrella of flamebaiting or trolling, but if there is other (and less US-centric) stuff of similar flavor going around, then fire up a Report thread with some links and point us at it so we know what we're looking for and can smack accordingly.
