"I've heard terrorism described as anything that is violent or has an economic impact, and shutting down a port certainly would have some economic impact. Terrorism isn't just bombs going off and killing people."
The article also mentions Critical Mass-style blockades as terrorist activities. It seems that any actions which impede commerce are terrorism, in line with the MPAA/RIAA's claims that file sharing should be punished as economic terrorism, and claims from various right-wingers that strikes and union activity are industrial terrorism.
(Isn't it strange that incinerating Arab civilians with daisy-cutter bombs isn't terrorism but protesting against it is?)