I didn't say anything about racism. I said that that blog post seems like sufficient grounds to call the author an "outspoken advocate of slavery" even if when that becomes inconvenient for him he says he isn't one.

And yes, he frames what he says as an exploration of Carlyle's ideas, but he's not just saying "Carlyle said this; isn't that interesting"; he's presenting his own opinions too.

As for whether believing that white people are (statistically, on balance) cleverer than black people makes you a "racist" -- which, again, was not what I was referring to above: it's really a question about the definition of "racist", and disputes over definitions tend to be unfruitful. For what it's worth, I would not call anyone a racist merely for believing that proposition.