So in psychology they break racism down into implicit and explicit. Basically subconscious and conscious racism.
The subconscious is about how you determine your in group as a toddler. So being around other races prevents it from forming along racial lines, but even seeing them on TV helps.
Grow up in a homogenous environment tho, it'll form along racial lines.
To prevent explicit racism, you have to use critical thinking, but in situations like you're example, someone reacts fast and those implicit biases against other races presents.
A stroke can damage the part of your brain that does that critical thinking, and suddenly someone "becomes" racist.
The details are important because we have zero control of what we're exposed to during our formulative years. It's literally out of our hands. And while we can over ride those biases most of our lives, even just normal aging makes them more pronounced.
But like, that shit where people kept blaming racist shit they said/did on popping an Ativan and staying awake on Twitter?
That has a valid scientific reason for making them say things they legit never would have normally.
Acting like implicit/explicit racism is the same just confuses those older people who are legit "from a different time" and is why they make such a big deal about how they're being persecuted.
It's terrible they're racist, but it's literally because they're losing important brain functions. I spent a couple years working with people with intellectual disabilities, they don't respond well to being yelled at, but if you break stuff down so they understand what's happening, everyone is better.
So, yeah.
Fetterman likely has always had implicit biases, but this isn't "mask off" this is a man who may no longer be capable of recognizing things on a deeper level than "you don't look like my tribe, you're dangerous".
Which for most of human evolution, was a big deal.
We just need to ensure future generations don't view their tribe as only people of the same race so this stops happening to them when they age or get fucked up.