The Brits and their off-spring societies didn't commit all that colonialism, imperialism, slavery and genocide because they were racist.
They became racist so they could commit all the colonialism, imperialism, slavery and genocide.
Racism was developed for specific reasons to acheive specific objectives, to justify and dehumannize in massive acts of a form of 'cannibalism'. To feast on the lives of others, build mansions with their bones, wear their skin in the form of cotton, sweeten cups of tea with their ground up bones, gorge on their empty stomachs in the form of wheat and potatoes. Justifying this massive cannibalistic feast of the 'civilised' christian man upon his prey with the basic logic of "not really human are they, not like us, and this is specifically why..."
Racism wasn't a straight forward idea, lot of thought went into it and the concepts involved evolved and altered over the British Empires long blood soaked history. US racism was born of that, French and Spanish racism was different, for instance in the America's Spanish capitalism and social forces didn't drive
massive amounts of Spaniards to settle in the Americas, so for them, once they got bored of sword-sharpening contests on live Native American children, they decided it was alright to mix with the natives afterall, they didn't have the same man-power coming from Europe to their colonies as the Brits did. So for them racism became much more a form of classism, with white elites rulling over brown and black workforces. Brit/American Racism was much more like the attitude of the aliens in Independance Day, and as an industrial resource. Anglo-Saxon capitalism, more voracious and expansionist beast apparently, probably not just the capitalism driving it though.
APOC probably haven't put as much thought, consideration and focus into their racism though, you can tell they are rank amateurs.
