My guess is the mostly the tone and the overly strong conclusion.
The topic is certainly one that is close to home for a lot of LWers and it seems to me we've heard almost all the variations. Then the tone, of a kind of artistic revelatory piece introducing lots of ideas only to dismiss them soon after, seems much more appropriate for a journalistic piece than the kind of deep logical thinking strived for here. Putting arguments in the reader's mouth and talking very patronizingly ("you're a picky one... my friend... this probably isn't going where you... (read more)
Pretty sure I remember reading Taleb on this, stating that homicides follow a normal distribution and he accepts Pinker's argument there. He de-couples this from the other kinds of violence, saying that the narrative stretches too wide--specifically warfare should be analyzed separately, since that follows Pareto distributions.