Kinda hard to say what's right or wrong. On one hand, it is personal property and similar to seeing someone left their headlight on in their car, motorcycle or moped, it would be proper to not touch it. On the flip side, some Hi power lights can result in serious heat damage if left on and you will do them a favor by turning it off for them.

It will depend on the surrounding. In a good area of low crime, I probably will turn it off. In shady area, I just as well treat it as hands off personal property.