The stereotypical Bernie Bro is one of those doofuses who spots a fedora and jerks off to Reddit all day, while spouting misogynist language all day, participating in toxic masculinity, spending most of their life at their parent's house.
LOL, get outta here. I could stereotype Hillary supporters as "dumb establishment shills who buy into an old hag's lies and deceit," but I wouldn't because that's not true. So don't do the same for Bernie Bros.
He's not saying the stereotype is true. He's just saying that it is the stereotype.