What concern is it of yours? Do you also flag down shitty drivers and correct them?
When I trained at work I had a guy stop me and tell me I was squating to deep. My first response was what qualifications he had. He had none. So I asked why he feels qualified to be dishing out advice? Nothing shits me more.
The problem I have with people offering out advice is how do you know the advice being offered is good? Half of the shitty shit you see in the gym is because of people offering up some Broscience bullshit, which spreads like a weed, because people like to look like they know shit, so they tell their mates. /rant