a LOT of leftish people online and particularly on Tumblr are really uncomfortable with biological analysis of cognition, though they wouldn't think so. Specifically, there is an extremely strong aversion to any idea which supposes that things can happen to a person out of their control which would alter their cognition such that they would change and develop anti-social, misanthropic, cruel, irrational or conservative thinking or positions. There's also a broader opposition to the idea that substances of any kind can change a person's internal thinking.
When one sees the reaction to it, one can't help but think that they are seeing - and taking a stand against - an attempt to absolve a person of moral culpability. And I do think that's what's going on here - I think this very sharp opposition to, for example, ascribing Fetterman's conservative turn to a stroke or irrational hostility to lead poisoning, comes ultimately from a desire to ascribe clear moral culpability (and, more importantly, righteousness) to individuals.
Theres also the opposite compulsion, which is to push back (correctly) on lazy voteblueish tendencies to say that boomers are stupid and nasty because of lead poisoning and when they die we will all be perfect little bodhisattvas. But even here you can see the shadow of an emphasis on one's personal responsibility for being upstanding and intelligent.
I recently saw someone say that there is nothing that can happen to you which would turn you into a reactionary, which quite frankly is obviously not true. From brain damage to TRT to lead poisoning to steroid abuse to tumours, there are many attested 'externalities' which can rapidly and shockingly alter a person's personality, often towards violence, possessiveness, and lack of empathy.
But, ultimately, that's what it comes down to - a strange emphasis on personal moral responsibility for ones positions. I think that this is tied in generally with the unfortunate contemporary tendencies to inextricably marry the political to the moral (and thus necessarily cast oneself as righteous). If I were to be uncharitable - and for a few people I am inclined to be very uncharitable - I would say that a strong motivator behind these posts is a desire to cast oneself as the Superior Moral Actor.
But what makes this especially odd is that this sort of individualist humanism is not really found anywhere in Marxist writings, which instead emphasize the broad tendencies of classes and the fact that ones internal cognition is entirely dependent upon ones position within the world. The idea that the individual can act without respect to history is simply anti-marxist.
Really, I just think people need to let go of this delusion that they have some sort of unmoved Self (previously called their Soul) which is prior to all actions upon their person or body, which acts upon the world through their body instead of being Of their body, and which must be weighed against a feather. If one is inclined to disagree, then I suggest they allow me to root around their prefrontal cortex with an ice pick, and see if anything about their personality changes!