One of his main points is that once you’ve declared yourself an “ist” of some sort, all kinds of assumptions follow.
Just look at what people assume about Bernie Sanders, for example, because he calls himself a “democratic socialist.” Or what follows when you describe yourself as a lot of other "ists" — a capitalist, a theist, an idealist, an opportunist. Or an atheist.
But I think the salient point that Tyson makes here is really perfect: “At the end of the day, I’d rather not be any category at all.”
That makes total sense.
(Full disclosure: I am an atheist, but I’m not one of the convention-going, agenda-having ones that he describes in this video. I just move through life without the need of a god.)