Yes it is, and opinions will differ on what crosses the line. Moderators decide, and any disagreement with the decision can only be expressed via a PM (to a different Mod, if desired). Arguing about it on the forum pages is considered a serious violation of forum rules.
If you see a bad post, use the “report post” triangular icon at the lower left. Do not quote it or reply to it with a bad post of your own.
This thread demonstrates how even “mildly” political posts cause problems, by triggering responses which are worse, in a chain reaction.