yes people can be soo mean and inconsiderate. my daughter ( now 17) has PWS on her complete left torso to her toes. She also has KT ( a vascular syndrome which was diagnosed at age 11. She's been an active all star cheerleader and danced in front of complete strangers in a crowd. I have to admit I worried sick about how will she handle issues... how will she hold her confidence as she matures... and basically her philosophy is "hey it's a birthmark, it's part of me, I would not change it and that's that!"
Please remember that 9 times out of 10 when someone reacts in an agressive way to you it is usually because they do not really know what to say.... and so they say something attacking or just plain ignorant. That my dear is their failure and issues not yours!
Stay positive, strong and just have a simple confident reply to give if needed during those time.
Good Luck to you!