For some reason I'm reminded of the line in Voltaire's Candide: it's a good idea to shoot an admiral every now and then, to encourage the others.
Good points but one percent of one percent is still a lot of people, e.g. about 30,000 Americans. You can't really execute them all and you don't want them in the police or armed forces (which is where many doubtless end up). Anyway, my comment wasn't so much directed at current policy, I'm just surprised that Asimov doesn't envisage more rational means of dealing with violent crime in his future world, or indeed of eliminating it from society altogether.