Why do strangers think they can give unsolicited advice designed to humiliate others?

This is not a post I expected to write but I wanted to put it out there because I know all of us that have dealt with weight issues have faced this one.

Here's what happened.....

Yesterday after exercising, I popped into the shops to do a top-up shop.  Coming down the escalator afterwards, an old man/stranger said to me "you'd lose weight if you walked down the stairs." 

 

Quick as a flash I shot back, "I've done my work out today thank you," to which he replied "I exercise for 30 minutes every day." 

Hmmmm.  Punch.  Counterpunch. Uppercut. Round 1 Over.

At this point, I realised this was about his ego, not mine, but it still riled me.

So I said (in my nice voice), " That's fantastic.  Michelle Bridges is my personal trainer.  I do at least 1 hour every day, 2 hours on a Saturday and then most Sundays, just because I feel so good, I throw in an extra workout.  That's on top of a 1 hour dog walk every day, rain, hail or shine. I've lost 32kgs so far.  If you need any tips or help I'd be happy to share them with you."

 

And I walked off (hopefully it was a Total Knock Out).  I have the ability - don't ask me how - to remain calm and pleasant in those situations while making my point but it still niggles and rattles me and gets under my skin that complete strangers feel they have a right to make not only a judgement about someone without knowing the facts but also to make a comment that has no other purpose than to belittle and humiliate the recipient.  Where do they get off?

After years of having comments like this come my way, I've learnt to handle them but to be honest, I get frustrated that I still haven't come far enough in my journey for people to stop making those kinds of remarks and although it doesn't affect me to the same extent or duration I still get angry.

My first instinct was to yell at him, "get lost you complete tosser" but I realise insecure idiots like him, that feel the need to humiliate others in order to make themselves feel better will always find something to say about other people's looks and behaviour. 

Have you ever had that happen to you and how do you handle it?