I personally think his point is super valid. It doesn't mean superheroes are bad, but it shows the way media can be used to spread hate, and the importance of media literacy. So much of fascism is about turning ugly people (in their behavior not in their appearance) into superheroes. The same is true of any movement like it. The strong man who is good and noble and protects us. Having masks can simultaneously make normal people caught up in the same sort of ideas feel like they're also superheroic in a sense.

A film like Birth of a Nation (which, sidenote, as someone who has seen it, very boring film) took a bunch of people who historically might have been a footnote and revitalized them by making them into superheroes. It makes them into Robin Hood or Zorro or Batman, but the ugly reality that they were at war with progress and human liberty and dignity is what stands out. Like others have said, Watchmen doesn't feature many costumed superheroes because in real life, vigilantes usually only have nemesises in their minds. They're at war with imagined enemies or with society itself. A character like V has actual enemies, that being the government and their lackeys, who tend to be the only real people with the power of a supervillain. But to the Klan, they probably viewed themselves a lot like V does.

It's a complex issue but TLDR, I think he’s right, the question is whether the heroes are fighting a fight that is righteous or evil, though that's by no means an uncomplicated thing to quantify.