Remote control and trespassing
First of all, this is a Remote Control device like the robots in Robot Wars, not an autonomous robot like the Terminator. It is operated by the owner via a standard RC car / plane transmitter.
Second, he is chasing people off his own property, not public property. It is not illegal to be homeless, however, it is illegal to trespass. The police would come by, chase people off and leave... 5 minutes later, everyone was back. The BumBot provides a way for him to keep people away himself by asking them to leave and only escalating to the siren, lights, and water cannon (super soaker) if they won't. In fact, most of the "regulars" no recognize the device and will leave as soon as they see it. While theoretically, shooting someone with water could be construed as assault, I doubt any judge would convict him and certainly no jury would.
Biting the hand that feeds IT
