This is an interesting question.
The answer is yes I do if they are young white guys or girls that look yobbish. This is of course all in the eye and mind of the person looking. The media has made us frightened of our own shadow, with stories of how mobs of young tear-aways attack people.
The truth is I don't think attacks on strangers is that common. The media has hyped us up into a paranoid society and we lap it up like a hungry dog. Why do we, as a society, want to hear about the horrible things that happen and not the millions of wonderful caring interactions that go on between strangers?
Food for thought.