Earlier quoted context omitted.
I think that's an unfair characterisation. I read it as the commenter using racism purely as an example where reduced diversity of opinion towards no racism is a good thing, not saying that all opponents of diversity are racist.
The commenter picked racism as an example, because they think viewpoint diversity is bad, and racism is a good example of a "bad" viewpoint.
Fewer people thinking that the Earth is flat would also be a reduction in viewpoint diversity.
OP has tried to make one point about the poor logic of the headline & you shut them down & refused to deal with the argument because you inferred the posit that racism is bad as them calling people who disagree with them racist. That's not you engaging with diverse viewpoints.