The author does not advocate validating factually invalid statements - see his anecdote in the second article linked in GP regarding "whether or not the economic collapse was caused by poor black people":
"I gave a quick response about how most experts would disagree with that assumption, that it was actually an oversimplification, and pretty dishonest, and isn't it good that someone made the video we just watched to try to clear things up? And, hey, let's talk about whether that was effective, okay? If you don't think it was, how could it have been?"
In other words - in the case of "bunk" it can be summarily dismissed with a proper basis. Which is entirely different from vilifying and personally attacking a person for their beliefs or thoughts which are doing no actual harm to anyone else. People can have bogus ideas and those bogus ideas can be completely harmless no matter how much you might find them distasteful.
Viewpoint diversity is entirely about bringing different perspectives and experiences to bear on a subject.
It works in the hard sciences: https://www.quantamagazine.org/20151124-kadison-singer-math-...
Why shouldn't it similarly be applied in areas of morality, ethics, social science, etc?