Investopedia explains 'Stock Basher' This is an illegal(!) activity that can carry significant legal repercussions (How do you look in road-crew orange, Janey?).
The basher generally benefits on how effective the negative rumors are, which can dramatically affect a stock's value. If an investor believes the false claims, he or she may sell off the stock at the higher price before it falls. The basher will then purchase the stock and ride out the gains.
Maybe the folks would like to hear from Brennan himself about all these things you profess to know. Here is his recent interview. I tend to believe a guy who brought companies to the Nasdaq and LSE over a a chat board basher.