You know, I've recently lost a bit of weight, all from improving my diet and exercise. I feel much better for it, more confident, happy - it will improve when I get down to my target weight.
Know what pushed me to do it? Me. When people gave me judgemental looks, it made me want to lock myself in my room and just stuff my face even more.
In my degree, we sometimes have to tell women that they need to lose weight, not just for their benefit but for that of their unborn baby. We need to learn to judge, without being judgmental. There's a HUGE difference.
So, you can have whatever opinion you want, but if you can't put it across in a civil, helpful manner, then you're better off keeping it to yourself as it could well do more harm than good.