I cannot stand food pushers, food criticizers, and food yackers. You don't need to tell someone how much to eat, what to eat, or tell everyone why you're eating something unless someone asks. It's just rude.
Overall though, it's best to let it roll off your back. It can be exciting, in a frustrating way, to have people tell you to eat more when you know they were staring at you thinking "step away from the burger, fatty" when you were heaver.
I think that excitement is what riles us up even worse. Just let it go. You know what's best for you, and if you don't, it's on you anyway
It has made me think, though, as an overweight person myself (have been most of my life)...it's going to be strange to be a healthy weight and see all of these overweight and obese people. I didn't fit in when I was fat as a teen, now everyone seems to be!! Sad indeed.