Graeber explores three areas of weakness among direct actionists, one of which was that they had a really difficult time dealing with a guy who was, in Graeber's estimation, probably mildly psychotic.
I bring this up because, basically, Graeber was saying that people were too tolerant, too accepting of very different people, too willing to let people who obviously didn't even understand what was going on attend meetings. For instance, the guy in question simply didn't understand what a 'block' was. He'd block everything.
He also describes the ethos of direct action culture as one where, rather than insisting that arguments must be won, that people *must* be won over and shown to be wrong, convinced to believe something else than what they went into the consensus building process believing. In fact, the argument is that, contra the statement above, the goal is to try to understand each other's arguments in the *best* light possible. The idea is to strengthen each other's position, to make their arguments better. In which case, the whole point is to understand one another.
I'd have to read the book in a hostile light again, to see if I can see what WS sees. But, at the moment, it doesn't square with my reading.