In the pictures the ones dressed in black with black face coverings are members of a faction within the anarchists. I provided a link to some of there intellectual discourse(warning:vulgar language and vulgar thinking are present)http://portland.indymedia.org/en/2007/03/356017.shtml
I think you just defined the whole of the leftist movement...
Thanks for the link crazyhorse...I may check it out when I'm in a better mood...