The point of those stickers isn't to ask for kindness. It's to let you know shit can happen on board and you may start driving like an idiot. Better stay a bit back so you have time to react.
If I remember correctly, the actual point of the signs in car windows is to alert emergency services to a child being in the vehicle in case the vehicle is in an accident. I could be incorrect however, it was just an explanation I heard decades ago at this point.