Didn't 4chan start off largely as castaways from Something Awful? Your point is valid though. 4chan had an enormous amount of time to become the shining star of how great an absolute[1] free speech site could be, but still manages to be a cesspool. This should be a neon hint, but people keep thinking that they're going to invent the one free speech site that doesn't end up toxic.

1: Also as others point out, even 4chan moderates, however lightly.