I get this shit every blue moon at the public gym. And it's always from some old fart with a gut who pretends to be a lifting guru. My response is always respectful, without raising my tone or acting annoyed. No need for me to make a scene in public and appear to be the bad guy. But hell, when you're shoulder pressing 90 pound dumb bells or chess pressing 120s, it's impossible (at least for me) to set the weights down completely softly without injuring yourself. There's always gonna be a little bounce off the floor, and it's never even nearly enough to cause a big thud that makes everyone turn their heads. But to some of these geezers, I'm "damaging the weights." Why would they care!?!? They never use the heavy weights anyway. And they're fuckin weights, not dinner plates. It's dangerous to even have a spotter try to take them off me after a set.
Most gyms have rules against dropping/throwing weights as part of their safety policies. But if the employees aren't saying anything about the way I handle weights, then other gym users ought to just mind their damn business and not interrupt my workout to try to lecture me.