[Erem]

They used examples where almost every reasonable American knows what the right and wrong side of history ended up being. He doesn’t need to teach us with detailed policy that slavers ended up on the wrong side of history — we all know.

[generalizations]

The point he's responding to is about epistemology - how the conclusion is come to, not what the conclusion is.

And 'wrong side of history' (bandwagon fallacy) and references to 'cruelty' (appeal to emotions) is really, really bad epistemology.