"My own belief is that laws are relevant only for defining the penalties for engaging in acts that virtually everybody agrees are wrong. When prohibitionists sputter, "so ... so ... should we just legalize rape because some people still do it?" they're missing the point. Rape is rightfully and effectively illegal because almost everybody in our society agrees it's wrong and should be punished. It also has a victim who generally takes great exception to being abused and is inclined to seek punishment for the criminals. Take a victimless activity and add a constituency that thinks it's a good thing and that the law is what's wrong, and you have the perfect makings for legal impotence."
He switches logical horses mid-stream here. First he makes the claim that, "Bans fail because enough people to whom the prohibitions apply refuse to obey them." Then he states that drivel above (or should I say he 'sputters' about it, since he seems to love that word, using it twice to derisively refer to those he disagrees with).
It's all well and good to make some high-minded claims about how we shouldn't legalize rape because we all feel rape is a bad thing. But he seems to forget he made the argument in the preceding paragraph that you can't prohibit anything because those who aren't inclined to follow the law won't bother following the law! There is no special clause there for bans where the general public accepts that a particular behavior is reprehensible.
This guy is just playing mental gymnastics in an attempt to come up with an argument to "logically" explain why laws or bans actually work sometimes - because if he admits they work, he undercuts his blanket position that there is no possible way gun controls (no one is seriously arguing for a total ban on guns anyway) would actually lead to a reduction in gun homicide.