I think the idea that if you don't know the basic names of something your opinion on it is suspect is a fair criticism. Especially with the very odd reference to a 20-round magazine. There is no state in the country where a 20-round AR magazine is legal and the standard-capacity 30-round magazine is not. Virginia has a 20-round maximum but only on handguns.

It should be acknowledged that the commenter is an avid NPR listener (nothing wrong with that) who doesn't have any skin in the game (something wrong with that, at least per his commentary).