It's less about 'who' it's coming from so much as what kind of (often blatant) rhetoric they're using. Which naturally does end up lining with and reflecting 'who' they are and what kind of per-established leanings they have.

A person who regularly circulates any NPC-like low-effort thoughts in their heads like that as some kind of 'gospel' on a frequent basis is clearly not someone who exercises a high capacity for original thinking.

And this applies to a zealots anyone can easily spot from wide variety of different groups, not just leftists.

And then beyond that I tend to take a moderately skeptical approach regarding peoples' intentions, especially when it comes to theatrics being played out in more public spotlights.