I think this conception mostly comes from newfags going to/b/ and then seeing troll and gooner threads and then conjuring up this insane mental image of what modern 4chan is. It's the same thing that motivated the routine summer /b/ threads of people trying to scare off all the gooners from the board. Those threads were almost always made by newfag teens, and it's the same thing with this conception of 4chan as a BBC worshipping gooner forum. Anywhere else on 4chan, you get actual 4chan, but /b/, as a result of being the most famous board, and the most lax board, has the lowest quality of content.
Also I blame greentext tourists. Fuck you creepswork, brendaniel, mr greentext, etc.