let me go saying its probably best just to let them have the wallet, you never know if they have a gun.
One of the reasons they know they can get away with muggings and nothing will happen even if caught.
But it is a vicious and complicated circle. You coudl fight back, be injured or killed by a weapon, or if you win maybe retaliation against you and family/friends. But most likely even if you do get hurt or killed, the scum would get a slapped wrist or be out in a few months maybe years.
Gone are the days when kids and people repected elders and each other, that's one of the reasons kids of today act in *** way they do.. I remember when random people used to tell us off, our parents did it to others, and everything was hunky dory. Nowadays you try and stop a kid or young group from drinking or smoking, making noise etc, they will harrass you, and then proabbly stab you.