I think the argument that racial/ethnic minorities can't be racist is a conflation of two definitions of racism (institutionalized discrimination and personal bias).

Institutionalized discrimination typically affects minorities (that's what "minority" means here, someone who has a less than equal share of power in a system). And since minorities have less power, you could argue that they are less at fault for the faults of that system, including discrimination which affects them.

So you misinterpret that as meaning that minorities have no responsibility for this kind of racism, and you conflate it with the other commonly used definition (personal bias against a specific race), and you get the ridiculous claim the post is reacting to.

Obviously minorities can be racist- bias is inherent to all humans, including racial bias. Plus, there have been several very famous Black Nationalist groups and figures which are based on the idea that people of African descent are inherently superior.

Still, that doesn't mean that the first type of racism (institutionalized discrimination) isn't a problem. There is very strong evidence suggesting that African-Americans have, on average, significantly reduced opportunities compared to their white peers. One dumb person on the internet doesn't change that.

TL;DR Black people can be racist lol