The website Crimethinc (Where that letter apparently originated) is written/ run by a bunch of die- hard Anarchist nutjobs who have no problem whatsoever using violence and domestic terrorism to achieve their goals.
They're the sorts of Anarchist losers who think of themselves as brave, fearless revolutionaries, yet whenever they start their explosions of violence and lawlessness (Or as they eumphemistically call them, "Direct actions"), they wear those stupid bandanas over their faces because they're too cowardly to reveal their identities, for two reasons: 1) To make it harder for the cops to identify and arrest them when they inevitably engage in vandalism and violence, and 2) To lessen the risk of their rich parents recognizing them in news footage of the protests and cutting off their trust funds (Another possible reason could be to hide how horribly rotted their teeth tend to be, due to meth- mouth).
In contrast, you don't see any Tea Partiers hiding their faces behind bandanas, because they have nothing to hide and not only aren't afraid of being identified, they want the public to know who they are.
I once perused a bit of Crimethinc's website for laughs, and discovered the following facts about them:
1. They think having any kind of personal moral beliefs is bad (I guess that way it'll be easier for them to sleep at night after terrorizing innocent people who may have committed the hideous crime of disagreeing with them).
2. They put up an article expressing a vehement opposition to bathing regularly and other forms of personal hygiene; In it, they claim that our society's love of cleanliness is just the result of propaganda by the EEEEEEEEEVIIIIIILLLL corporations that make personal hygiene products (I am dead serious here, the article was called "Washing and brainwashing" or something stupid like that).
3. They also put up numerous articles completely justifying the use of violence in their actions.
So, in other words, to the Crimethinc freaks, bathing= BAD; Violence= GOOD.
Fortunately, the fact that they felt the need to write this open letter to the OWS crowd is a good indication that, as stupid as the OWS'ers are, at least they're not going along with Crimethinc's demented views. I'd take semi- passive, pot- smoking hippies over violent, meth- addled Anarchists any day of the week.
I'm reminded of the scene from 'The Chronicles of Narnia; Prince Caspian' when the heroes refuse to accept the help of a vicious hag and werewolf, knowing that even in their struggles, there are some lines that shouldn't be crossed.