Locks, and bikes are cheap. You do not want to be the one who escalates the situation PERIOD. He said he was going to beat him up, what are we 5th graders again? next he would probably comment that your mom was fat. If you have a picture of him (or video) show it to the cops. They won't be able to do anything, but you will have done your part.
There are times to let the sheepdog out, but at other times you have to make it heel.
There are times to let the sheepdog out, but at other times you have to make it heel.