If that horse is as young as it looks from the picture those people should be horse whipped. A baby's bones don't fuse until their 2 yr old year, and the damage they're causing will ruin that horse for life. Not to mention a babies attention span is about 60 seconds.
At that age I might throw a blanket over their back (from both sides) when I'm grooming/handling it, but thats as much weight as I would put on a baby. The other thing, you see people do it all the time because they're scared to throw their leg over; hanging on the side of a baby is really hard on them. These people have no business with a horse, unless that horse is 3 or 4 and just looks like a baby, but i don't think thats the case.
