I think what they are saying is a common sentiment among people who don't belong in any of the major political camps. It's a common experience to take heat from all sides because, surprisingly, neither "side" in politics is perfect nor particularly virtuous.

But we're not criticizng him for not registering for the democratic national convention or the republican one or whatever you think "belonging to a political camp" even means (what does it mean, exactly?)

He's being crticized for repeating lies and refusing to post truths.