Like the terorist phrase - most terrorists are Muslims but not all Muslims are terrorists.
As it is with the hoodie/BB cap wearing, the thing that struck me about the footage of the London riots, most, like 90%+ were wearing hoodies or some article of clothing to cover their faces.
So my analogy is "Most ar*eholes wear hoodies/some other means of disguising their identity or intent, but not all hoodie wearers are ar*seholes."
Just those ones drinking xxxx wearing white sox and have long ranga sideburns.