Argh, how annoying for you. Can you just ignore, or set up your bar for, ooo 80kg, get up close to him the next time he does it, and say "Mate, just squat that bar or fuck off."
At my gym - where men and women use the free weights, although last night it was mostly blokes - a commercial chain gym, but really friendly, people of all ages & a lot of active PTs, I'd probably go to the manager or front desk, and ask them to keep an eye out for the guy, or have a quiet word.
I tell you want though, I was doing my sets of squats last night and I was squatting 40kg (I'm not too much of a beast like you @Bubblemonkey, sadly - I only get to around 60kg as my top weight for squats!) and trying to change the plates & could I get those bloody safety catches back on the bar! Strong af, but can't manage the safety rings. I could have done with an interfering bloke, even with the embarassment of it.