One major reason I'm sceptical of this is that, at 6 months of age, babies aren't actually capable of knowing what they look like.
Well, it's not what studies have said.
Even then, type in "babies are racist" in a search engine, and you'll see the results.
Because again, they don't always align.
The most famous example would be the Clark doll experiment (although the Clarks actually did a whole bunch of similar experiments). If racism were motivated by in-group bias, then black children should assign positive value to dolls that have a similar skin and hair colour to them, but the experiment actually found the opposite, as has almost every experiment looking at racial bias in children. Black children replicate the negative associations and feelings about blackness that they encounter in their lives and the culture around them, and they do so at a developmentally crucial stage which informs their expectations of how they should be treated and how they should treat others. That is a racial bias.
I don't know exactly how that disproves the idea of racism being motivated by in-group bias. What you're describing seems to be internalized self-loathing. On the practical sense, in real life, the black children will show a preference for people who look like them, same as most groups - we (and by we, I mean all humans) tend to self-segregate. That isn't racism ipso facto, but it's a common factor.
I really can't be bothered to go through each of those examples. In fact, looking at them, I was reminded of all the examples I left out, and far more modern ones at that.
The idea that all of this can be attributed to "one system of thought" doesn't hold water, neither historically or contemporarily. Even if we say, for argument's sake, that racism is racism, and everything else that I'd call racism is really "racism-x," even if we get rid of all the "racism," that won't do a damn thing to get rid of the "racism-x."
..and assuming that is true (which is a stretch) why do you think they think that?
Don't give me some bollocks about "alternate ways of knowing" or some misquoted phrase you stole from a rantsona video. This is a specific claim, I want a specific answer. Why do these people think, definitively, that 2+2=5. That's a weird way to think, and I'm sure an open minded and intellectually curious person like yourself was fascinated to find out the reasoning behind it.
Well first, the idea of "alternate ways of knowing" was introduced to me through various online publications, and not ones you'd call fringe by any means. I'm all for "alternate ways of knowing" when they've been verified to work. For instance, firestick farming in Oz is a proven method of reducing bushfires, so go for it, definitely. On the other, you'll never get me replacing "sixty-thousand years" with "time immemorial" due to "the failed concept of linear time" (yes, that's an actual quote).
Second, if I had to guess why people said 2+2=5, I'd boil it down to the following:
1: Trolling, or to be more precise, "sticking it to the man"
2: Postmodernism, or at least, the idea of there being no objective truths (as we've seen on this thread), so therefore, any mathematical formula becomes valid.
3: A general decline in mathamatical proficiency (this is true in Australia, it's true as far as I'm aware in the US), and a strain of thought that has resulted in the lowering of maths standards rather than trying to increase proficiency. We've seen this in the US in various areas with the gutting of advanced maths (and other) courses, usually in response to them not representing some arbitrary representative demographic.
No, it's actually not.
I'm going to be very clear. I don't agree with what was said there, at least not in the immediate sense, but it's not racial determinism and I'm confused as to why, outside of intentionally hostile reading, you would assume that it is.
Believe it or not, it's not an intentional hostile reading. I've seen this strain of thought pop up in various places, including here.
Even if it isn't racial determinism, what do you think is the reason for disparate outcomes? I think culture can play a role, but would you agree that poverty is a reasonable explanation?