Most people were shocked that the guy felt he had the right to comment on someone else's body regardless of the context, with the top response being:
"Report it to your gym, he had no right to comment on your body at all, and no right to try and assert his 'help' onto you, if he can't control himself from staring at another person's body then he shouldn't be at a place where he's going to encounter all manner of bodies."
A lot of fellow gym-goers also pointed out that wearing a bra might not have prevented the issue, with one person writing:
"As someone with boobs, sometimes your nips show through a PADDED bra. I've never worn a sports bra that didn't headlight people pretty much the entire time I had it on. His argument doesn't even make sense if you know boobs work."