My reaction would have been to draw my weapon and counter the person pointing a gun at me while loudly announcing "Drop your weapon"...
"Don't worry man, it isn't loaded" doesn't cut it... and getting away with having a weapon pointed at somebody will only make them think it's okay to do it again. The "adult" with the crowd would probably had to carry his teeth home in a bag too.
We live in a society that is now fraught with dangers... not just from stupid people, but from real threats, and a weapon pointed at you isn't imaginary. If we have learned anything from incidents like Virginia Tech and the high school shootings, it's that you have no idea what's in somebody's mind that is holding a gun and pointing it at you.
Kids today are playing video games and "killing off people" all day long, and it isn't much of a transferrence for them to act stupid and not relate the actual danger of pointing guns at people in the real world. Talk doesn't stop bullets... and as a self defense instructor, I teach students that you're obliged to defend yourself first, and talk things out later. With firearms, it is entirely possible you won't get the chance to talk.
At a public range, I would have put the guys on notice... and found out why the rangemaster wasn't keeping up with what was going on... but luckily, you didn't get buzzed while this "empty" gun was pointed at you.
Years ago, I had a friend who took his guns to the range and blew a hole in the roof of the shooting stand with an "empty" gun. He had left a round in the chamber and simply decocked his pistol when putting his guns away on his last trip. In attempting to take out the magazine, his finger pushed down on the trigger, and the rest is history...
I handle guns all the time... and the FIRST rule is "don't point them at anything you don't want to shoot"...
Rule two is that "stupid comes in all sizes"...
You were lucky... and those guys SHOULD have been thrown off the range. I'm sure they would have been "sorry" if they had accidently shot at you. When people "flip me off" like that, I always blow them a kiss... They were just lucky you didn't draw down on them and put a few rounds in their direction.
WT