FWIW, I've always understood the referent for "politics" in "politics is the mind-killer" to be, not political principles or opinions (which in fact get discussed here all the time, typically civilly and sometimes usefully), but tribal affiliation with powerful governmental/nationalist camps. I often refer to it as "partisan politics" for that reason, and around here I sometimes refer to it as "Blue/Green politics." (Both formulations of which neglect the nationalist aspect, but not for any principled reason, just for convenience. If the Blue/Green teaching-story had included a neighboring nation known as the "Purples," I might refer to it as "Blue/Green/Purple" politics.)

We would presumably find partisan religious discussion equally problematic if we didn't already filter for alignment with a particular camp.
We do find sex/gender discussion problematic, I think for similar reasons, and would find it much more so Less Wrong didn't filter for a particular gender.
We similarly find race/ethnicity discussion problematic, though for the most part it doesn't come up... there's one member who periodically talks about how some races are superior to others, and that causes a certain amount of turbulence before it dies down.
Etc.

In general, if we believe there are powerful groups or entities fighting for control over large-scale decisions that affect our lives, we tend to pick a side and invest emotionally in supporting whatever positions are conventionally associated with that side, and signalling considerations start to predominate. This makes analysis difficult.