Yeah, at the core, people cause problems when the group gets too big to be a tight knit one. There are also a not insignificant amount of people, who get together, with antisocial behavior in mind. When you have thousands of people, posting on some community forum, it will be impossible for it not have some serious underlying issues. Not to even think of the scale of places like reddit, where that forum could have millions of users.

Back in the day, when IRC ruled the social scene of the internet, it was hard to control a channel that had 100+ people on it, forget about crowds orders of magnitude larger.