Graeber was a member of the group that conceived Occupy in the first place. As an expansion of the previous post, here he provides a rebuttal to Chris Hedges and a handy primer on Black Bloc protest tactics.
“Diversity of tactics” is not a “Black Bloc” idea. The original GA in Tompkins Square Park that planned the original occupation, if I remember, adopted the principle of diversity of tactics (at least it was discussed in a very approving fashion), at the same time as we all also concurred that a Gandhian approach would be the best way to go. This is not a contradiction: “diversity of tactics” means leaving such matters up to individual conscience, rather than imposing a code on anyone. Partly,this is because imposing such a code invariably backfires. In practice, it means some groups break off in indignation and do even more militant things than they would have otherwise, without coordinating with anyone else—as happened, for instance, in Seattle. The results are usually disastrous. After the fiasco of Seattle, of watching some activists actively turning others over to the police—we quickly decided we needed to ensure this never happened again. What we found that if we declared “we shall all be in solidarity with one another. We will not turn in fellow protesters to the police. We will treat you as brothers and sisters. But we expect you to do the same to us”—then, those who might be disposed to more militant tactics will act in solidarity as well, either by not engaging in militant actions at all for fear they will endanger others (as in many later Global Justice Actions, where Black Blocs merely helped protect the lockdowns, or in Zuccotti Park, where mostly people didn’t bloc up at all) or doing so in ways that run the least risk of endangering fellow activists.