It's too bad that groups of crows got stuck with this unfortunate name. Crows are no more violent than most other birds and probably less so than squabbling house sparrows, though I will admit that they do prey on the nestlings of other birds (who prey on the larvae of insects, so they've no real right to complain). I suspect the term came from crows' scavenging habits, a human corpse on a medieval battlefield being just so much roadkill to a hungry corvid.
Today I was privileged to see entire fields of crows as I drove along Route 36 in eastern Ohio. All the corn stalks have finally been cut down, and every field had its complement of black birds, eagerly checking for missed kernels and late insects. I was hoping to see them rise in a great dark cloud and go swooping off into the sky, but no such luck. Crows are practical creatures. A cache of food and the company of a hundred or so of one's closest friends are blessings not to be ignored.