Eh, if by tankie you only mean literal communist tankies, that's just a single aspect of human nature.

There's absolutists, extremists, and (frankly) sociopaths in every political/ideological grouping. The more you get towards an extreme, the more you run into militant examples of the group. Tankies are just the communist bloc of the crazies.

But, there's folks like me that are all for revolution, but draw the line at unlimited killing to achieve it, or the eradication of groups in the name of the cause. I'm an extremist by most peoples' standards, but they've never been exposed to the real crazies of any extremist bloc.

You run into the bonkers adherents of communism, anarchism, nationalism, or religious extremists, and they're essentially the same mentality because it's a human failing that some of us are willing to kill indiscriminately for a belief. We're just lucky that that degree of extremism is split up, keeping them from being a serious, constant threat rather than the intermittent threat that they are.

Seriously, if you ever spend time around people that are working towards a goal like a change towards socialist thought, you'll run into the batshit ones on the edges. You hang around the wrong places, you'll run into right wing militants as well. They, none of them, are avoid knowledge, judgement, or reason. They're zealots, and they'd be the same no matter what ism infected them because it's about the fire, the anger, not the actual thing they're using as their obsession.

Fuck, I've met a couple of people involved in pacifist movements seriously express the idea that "we" should just rise up and kill until all the warmongers are gone. People, humans, are always going to have zealots like that, no matter what.