Ever been a teenage girl?
I’d assume they could reasonably have had fear for their personal safety - strange men in an SUV trying to pull them over late at night. You say they had “nothing to fear” - well, if you call potential kidnapping, rape, and murder nothing then I agree.
I said nothing of the sort. Maybe they were frightened. If so perhaps they will quit wandering around the neighborhood late at night in the future. The fact is the men didn't want to “kidnap, rape, or murder them”, and they assumed wrong if that is what they thought. If you think it's ok to shoot anyone you “think” might want to harm you, then you are wrong too. The girls father will have to pay the consequences of his and his daughters wrong assumptions for the rest of his life.
Personally, I think the girls were breaking into cars, and were angry when confronted and so one of them fed her father a line in order to get even.
Finally, one small point. The girls were on foot when the neighborhood watch guys questioned them. They then went to their car. The neighborhood watch guys didn't try to pull them over once in their car, they just followed them and then drove on once they reached the girls home.