Take this maxim to heart: Self-defense is not about winning fights with aggressive men who probably have less to lose than you do.At the risk of invoking the naturalistic fallacy, I'll point out that Harris' prudent advice is not just applicable to humans, but exists instinctively in other parts of the animal kingdom. When it's time to stone the crows, take a cue from how raptors deal with them:
A red-tailed hawk, of course, could dispatch a crow in as instantly as it could get a talon on one. But the payoff is nil (for whatever reason, birds of prey don't eat them--vultures won't even take them as carrion), and it risks injury in doing so, especially if it's being pestered by a murder. An injury to the hawk is potentially fatal because of how he feeds (like a prominent lawyer being arrested for escalating beyond the legal notion of self-defense and making some hothead pay for trying to be a tough guy). The crow mostly scavenges so doesn't need to be as careful, even if he's aware of the hurt that the hawk could put on him (and he's probably unaware of it, anyway). The hawk has nothing to prove and nothing to gain from engaging the crows, so he just evacuates.
Parenthetically, the second part of the video is fictional narration by the person who captured it. This isn't the same bird (if it's a hawk at all, it's not a red-tail) and it doesn't give chase to the crow, it's simply leaving its perch as soon as the coast, er, air, is clear.