I mean that's pretty vacuously true, since (the community of) "4chan" is a subset of (the total population of) "humanity in general," but it's a stronger and more interesting claim to make about the subculture in question.

If anything, the person you were replying to was intentionally describing how 4chan is less dissimilar to humanity in general than its typical portrayal, so responding with a dismissal that that makes them just the same as everyone else is really just affirming their point.