This is a question and i'm not trying to dunk on the tweet
I thought the main reason why those were bad because it mocked black people and they were the target of the ridicule, and while Cohen uses a similar technique in Borat he is targeting Americans as part of his satire, not Kazakhs.
I saw a criticism in vein of "People he can mock by making them think Kazakhs are actually like this would also believe that there is a country called Loftristan and its people act like that" and i can accept that, but comparison to blackface makes almost zero sense to me.
I think there is a significant amount of viewers who don't pick up on the satire and just think Borat's character itself is funny. Or they do pick up on some of the idiocy around him, but don't really care or think it's as funny (where for us that's the main focal point).
Cohen's type of satire isn't going to resonate with a lot of people who see it as him being racist for a joke, which is never acceptable to them, even if the "primary" joke is not the racism. It's like the (completely valid) take that cumtown needs to stop using the n-word (or even the phrase "the n-word") or similar content as joke material, since it just crosses a line that doesn't need to be crossed. (Though nobody asked) I disagree with this taken but I do think it's totally valid, and that "well it's just a joke/satire" is a flimsy defense.
On a semi-related note, the original-tweeter wrote a book called "Twitter and Tear Gas" that's pretty decent (it's available for free online). She has been a part of OWS, Arab Spring, and Zapatista protests over the past couple decades, and talks about the influences social media has had on each one. A lot of us are terminally online, so maybe it's less interesting to most, but I also think a lot of us aren't actually involved with any sort of direct action (IRL or with online support). Anyway, I'd call her a good-lib, but expect some bland takes about Hong Kong and that sort of thing if you follow her.