Those snotty bad-excuses-for-a-human beings remind me of my needlework teacher. Whenever she saw any of my "work" she got struck by disgust and a sound like Arrgh with a slant toward puking came out of her painted mouth.
At the end of my school days all my peers, my mother, father, brother and all my friends knew that I had two left hands - including me.
When my mother visited me at age 40 she watched me finish curtains for my living room. I pretended not to notice but I saw her surprise.
At night she realized that she had forgotten her PJs. I gave her a pair of the ones I had made. Another surprised look.
Next day, as if it had been ordered, my neighbor came over and said, "Come over and help me with my shelf. I need a pair of hands like yours." I grinned when I quickly went over there to help (and have fun doing it).
That's when my mother finally started her comments with: "You know, this is strange ...."
When some bitchy knowitall says something inappropriate to me then I just grin (I have years of practice with that).
But I hope you will remember all the great retorts whenever you see one of those big-mouth-hyenas assault a child - and let them have it.