AFAIK this is completely legal on BFL's part, it also makes perfect sense for BFL to do this.
Given that BFL's business will flounder without generating pre-sales to fund their production, they need to continue collecting new investors. They can't collect new investors if the old ones fill these forums with complaints. If Wired or Ars Technica stumbled across one of these threads full of BFL pre-orders shouting and brandishing their torches & pitchforks then BFL is toast.
By publicly evicting a few outspoken critics, they hope to silence the complaints of their pre-order base. If the complaints swell to a critical mass, people might start asking for their money back en masse and BFL cannot abide that.
Plus, Josh's ego won't let the sort of things the OP said pass without some form of retaliation.
In other news, Avalon batch 2 is shipping.
P.S. Maybe you could ask Avalon to sneak in 1 extra unit into batch 2 for you. It might be a PR coup for them 
Wow, that is a very good idea....