Long ago in many technical chat areas and professional forums they would ban politics and religion to prevent arguments.

There is nothing wrong with banning topics in a sub as long as you are open, honest, and public about it while being clear enough that there is no misunderstanding of what is banned discussion.

This permits users to avoid discussion of topics without the risk of facing a ban

What I have a problem with is mods not being open about banned topics, running a private blacklist for wrongthink, permanently banning users without warning then claiming they can't tell you specifically what is the violation. The injury is the ban, the insult is not being honest enough to tell you exactly what the violation was.

There is nothing wrong with banning topics in a sub as long as you are open, honest, and public about it while being clear enough that there is no misunderstanding of what is banned.

This permits users to avoid discussion of topics without the risk of facing a ban

What I have a problem with is mods running a private blacklist for wrongthink and permanently banning users without warning then claiming they can't tell you specifically what is the violation. The injury is the ban, the insult is not being honest enough to tell you exactly what the violation was.