Last night's anti-police-brutality march—a chaotic brew of nuisance vandalism, bickering among participants, and, yes, reports of heavy-handed arrests—was maybe more useful than it seemed in the dim glow of all the talk of smashed windows and hyped news releases. (H/T to Jess E. Hadden for the Ustream video above.)

It's brought back to light, on a local level, questions about the permeability of Occupy's message and massing—and the relative ease in which groups whose aims run counter or even merely neutral to the movement's overall focus on economic inequality can wind up distorting public and media perceptions of all the inchoate aims the Occupy movement is actually all about.

In this case, it was the return of the Black Bloc-style of petty destruction/protesting Portland has long been familiar with but which had largely been absent from most mainstream Occupy events. Tension between the factions has been simmering for months—I remember hearing about it during the November eviction of Occupy's downtown camp and actually seeing it outside Terminal 5 during the Port of Portland protest in December.

But last night it bubbled over—and like with so much of Occupy Wall Street, what happens in one town is often a reflection of what's happening nationally.

It's a fight that seems to be coming to a head everywhere.

To wit: A column yesterday on Truthdig, by Chris Hedges, ripped into Black Bloc tactics as a "cancer" on the Occupy movement out to hijack what it stands for.

Solidarity becomes the hijacking or destruction of competing movements, which is exactly what the Black Bloc contingents are attempting to do with the Occupy movement.

“The Black Bloc can say they are attacking cops, but what they are really doing is destroying the Occupy movement,” the writer and environmental activist Derrick Jensen told me when I reached him by phone in California. “If their real target actually was the cops and not the Occupy movement, the Black Bloc would make their actions completely separate from Occupy, instead of effectively using these others as a human shield. Their attacks on cops are simply a means to an end, which is to destroy a movement that doesn’t fit their ideological standard.”

But that was written after members of Anonymous posted a creepy video in late January that all but declared war on the Black Bloc, warning them against the kinds of provocative tactics that police forces might cite if and when justifying rough, violent arrests of protesters looking to maybe block a street (which, no, is not violent) but not do any actual property damage.

Update 4:30 PM: And don't think this stuff isn't coming from both sides. Here's an Indymedia post in which someone says occupiers ought not to be allowed into radical groups' marches.