A forum not populated with aristocrats will be degenerate unless it's mono-tribal. Aristocrats can be cosmopolitan; peasants cannot. It will be full of foreigners, and foreigners are for being attacked. Most of the peasants won't even realize it's not on purpose. They're just different. Fora will quickly get a reputation for being full of "trolls" which will be a self-fulfilling prophecy; only trolls will visit. It will become a war zone.
In the usenet days, it was monocultural and aristocratic. It was a subset of a subset - successful university applicants only, explicitly filtered for high IQ, and only those who bothered with the computer labs. This produced useful fora.
Having public signups is just a bad idea unless you enjoy pointless word-only warfare.
Fun fact: AOL's headquarters is in Langley. They're literally a CIA spinoff. The internet was vandalized on purpose.