Racism is more than some people not liking your particular skin color on Twitter. Being black means every police encounter is potentially lethal––see today's news, or that jogger two weeks ago for recent examples. People call the cops when you're birding in Central Park, and unless you're lucky and have a recording, they aren't going to believe you.
If, perchance, some virus starts going around, you'll find the hospitals in predominantly black neighbourhoods have less staff and equipment, and the 30% black people in your city make up 60% of the dead (Chicago, Detroit).
In other words: it's systematic, and about power. That stuff on Twitter is stupid, but it isn't equivalent.
That does not mean that anti-white racism should be acceptable.
It's a pretty simple concept.
I legitimately want to know what's up with Twitter allowing these comments. I find it weird cause it'd go without saying that hating any other minority would land you a ban or suspension.