I have lost and regained twice. When I regained, I didn't quite reach my peak but I was way too close for comfort. Now that I have lost it again (and maintained for awhile), a lot of people think this is the very first time I ever lost weight. Even people close to me, like my parents, wouldn't remember that I once (or twice!) regained it. So, they don't quite get why I can be so vigilant about my eating and exercise habits.
No one ever really directly confronted me about my weight regain and I honestly doubt anything they said would've helped me.
I've never been one to base a person's personality or moral fiber to whatever their number is on a scale. I'm not particularly smarter now that I am in maintenance mode than when I was regaining. Life changed and I couldn't handle the change while maintaining my weight.
I find that people who are near or at goal weight will be more receptive to diet and exercise assistance or advice. So, if you have a friend who lost a lot of weight and is now getting married or having a child, you can offer to exercise with them during the next year or so for encouragement. Or give recipes now that she will have less time to cook, etc.
It becomes an issue of prevention.