Good points.

If the driver's side window had been smashed out - that would be different. But it was the passanger's window. Even if he had reeeeeally long arms, he wasn't trying to joke the guy. I think the man just wanted to mess up his car. That's hardly self defense.

I think people that carry large sums of cash (people who have to make nightly deposits) or property (as in your friend's case) are perfectly justified to carry a weapon.

Personally, I think that most normal people, if they follow common sense would never have to carry a weapon.

Smashing windows is stupid too.