Inmy opinion they shouldn't have called 911 in the first place. It's not like you were waving it around. As you stated its holstered on your hip. If people think a holstered gun is dangerous, then so is a parked car.
Ok so they call 911 and the operator asked what are they doing? They respond: Just walking down the street witha holstered gun. It's non threatening, and that just seems like a waste of time to me. You're doing nothing wrong and they can't do anything about it.