There are communities where you pick the people who are associated with, and communities where you don't get to do that (or do it as much).
The internet gives you huge control over picking communities that think/have interests exactly like yours (and that's exactly what the parent was mentioning to like about the internet communities).
In real life communities that are not e.g. a chess club, but more like neighborhood, school, etc, you are forced to live with, and deal with, all kinds of people, not just the one you chose to. At best, you can move to a different location, but you still don't have the control to pinpoint and seggregate interests the internet gives you.