Ouch. Sorry to hear that. I'd go ballistic (no pun intended). I don't think a gun range is really a smart place to piss people off, especially an unregulated range in the hills.
Though, I would not bring much more than clays and maybe wood target stands and paper targets to a place like the Glass Factory. Your experience goes to show how people there act and the uncertainty of leaving with your property in one piece.
Might I also add anyone who visits Glass Factory should bring a trauma kit with them. I'll be grabbing at least one IFAK if I go up Monday morning for memorial day, as I'm sure it will be crowded.