He's supposed a scholar, but he can't even name his source--like TRump pulling stuff out of his butt--same with the black scholars Zizek ostensibly and ostentatiously refers to; BTW, this is his form of virtue signalling in this video.
He doesn't need a source. The examples stands on it's own. It's not argument from authority (the authority of the offended party). It's argument from internal logical consistency. It doesn't matter whether his native American friend (who he may have made up) really prefers the term Indian or not. Anyone can follow the logic of the statement.
Remember, Zizek isn't woke. He doesn't care who is offended. He doesn't care how many Native Americans are or aren't offended by his jokes. Their offence carries no weight for his behaviour. Only in the woke world do people bend over backward in order not to offend various groups.
As far as sources for his philosophical views, he also doesn't need that. He is a Lacanian. But he's done enough work, and introduced enough unique thought now, to stand on his own.
Wokes often try to dismiss him on moral grounds. But it's obvious (to me) that it's intellectual laziness. Following Zizeks trains of thought requires actual effort and usage of brainpower. Kneejerk reactions and feelings is much easier. So wokes often go with that. But there's no thinking going on. If you want to dismiss him, you'll have to actually make an effort. Sorry about that.