Woops, no it isn't. The use of deadly force to protect property is only authorized in Texas and in any state you are only allowed to use force required to prevent the robbery. Since these kids had already given up their attempt, moved somewhere else and started acting like they were waiting for the bus, the attempted theft had already been prevented. Since the theft had been prevented and was not imminent there was no privilege to use force against them.

You had a good point about the name calling, though. If someone had tried to steal my stuff I'd be calling them all sorts of stuff, too.