The net effect of a moderation policy like yours is further entrenching of the status quo, since that's always the most "polite" opinion. Any challenge to power structures or other entrenched ideas is always read as "impolite", because that's how power reacts to a challenge.
If you go by how badly other commenters behave, how vitriolic various replies are or you feel they are, and so on, that's a recipe for a downward spiral, because literally everybody feels that way. I'm not saying everybody behaves equally badly (that's not so), or that everybody is equally right on the issues (also not so). I'm saying that everybody is subject to the same cognitive biases, which have hugely distorting effects on perceptions and therefore on behavior.
One of these biases is that we evaluate our own behavior in one way and other people's in a completely different way. I've been describing it this way lately: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...
Another bias is that our image of the group is determined by the datapoints that we notice and place the greatest weight on, and those unfortunately tend to be the ones we dislike or find painful: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu.... That means that people have a distorted tendency to see the group as worse and more hostile to themselves than it really is, which leads to a "why bother" and eventually a "fuck it" sentiment which you seem to be feeling when you say things like "I've long since noticed that being polite doesn't matter here". The problem with these perceptions is that they end up creating the very situation they feel they're reacting to.
The solution is to prioritize taking care of the commons, no matter how badly others are behaving or one feels they are.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and sticking to the rules when posting here, we'd be grateful.