Pete Guither's theory:

People see violence on the street and say "that's because of drugs" when, in fact, it’s because of the drug war. And so they call for more enforcement even though (as we know) that won’t help the problem but rather make it worse. And, quite frankly, this issue is much more visible out on the streets in poor/minority neighborhoods than in affluent neighborhoods where the drug trafficking takes place discretely in the country club locker room.