I run a small politics forum. I was able to get down to one rule that seems to work.
No ad hominem or insults of any groups, people, or policies. People can talk about why they like things or why things will or wont work.
People continually try to work around them and sometimes there are comments that are borderline. Most people are very respectful and libs and conservatives can debate.
An example of trying to bypass is someone calling trump a Nazi. this is obviously meant as an insult. The person claimed it was a statement of fact. Trump has never identified as a nazi and therefore it isnt a statement of fact but is simply an opinion meant as an insult.
Once the insults were removed the group functioned well.