Except the paragraph included "marginalized groups can be just as prejudiced as privileged classes". Which you'd know, had you actually read it.
...The fuck?! Claiming that anyone who's not "privileged" can't be racist or sexist, only prejudiced, is exactly how that logic works.
Everyone gets caught up in this dumb semantic argument. The actual claim is really simple and fairly sensible:
There are two kinds of what we could call "prejudice":
1) Embedded social attitudes, stereotypes, tropes and whatnot. This is reflected in loads of ways: everything from longer sentences for black criminals than white, women not getting as much credit for work as men, and crappy racist legislation. It's also reflected in media and words and shit like that. AND
2) A person consciously hating another person because they are a certain ethnicity. Or using institutionally racist memes to humiliate another person.
The latter is the sort that people remember. The argument is that the former is where the money is, and the latter isn't really that big a deal.
The next step is realising that the word racism has some sick salience and trying to exploit it for good. Not complicated.