This is a quite ludicrous extension of the principle of presumed competence.

Making a claim on the basis of a presumption that one race or another is comprised of idiots is, of course, both highly offensive and highly wrong. (Aside: it's also offensive, though perhaps less so, if you assume it about some other group, like Trump voters. About Big Lie folks--well, no, you can "assume" it about them because it's not an assumption: by buying into the Big Lie which is a very very well documented, um, lie, they're documenting their idiocy and/or duplicity.)

But you seem to be positing that skin color makes people so bafflingly incomprehensible to each other that they can't even understand what evidence looks like about people in other groups being misled.

That's pretty silly.