How do you determine if they are mentally convincing themselves they are the good guy, when in fact it is you who is the good guy.

From either perspective, if the roles were reversed, wouldn't it look the same? Both parties thinking they are doing the right thing.

There are a lot of legitimate criticisms out there, they seem to be vastly outnumbered by illegitimate criticisms, no matter what position you hold. It's easy to hold your opinion when you are inundated with a constant stream of invalid arguments that say little more than "I don't like the tribe you chose". Any valid argument is easily overlooked without a sense of guilt in that environment.