One of them is people's tendency not to be aware of the negativity in their own comments (harshness, provocation, etc.), while at the same time being super aware of it in others. This skew in perception leads to the feeling:

"I am a valuable contributor, sharing insights and questions; you are a shameless troll, spewing drivel and aggression."

And its cousins:

"Me? How can you moderate me? This is bias and censorship of the worst order."

and

"Ok, I may have overstepped a little, but the other started it with their obvious abuse. Am I not supposed to defend myself? You obviously must agree with them."

In the case of divisive topics "I" becomes "we", a.k.a. "my side", but the dynamic is basically the same.

All this is human nature so it's kind of hard to do anything about.