kungfupannda -
that is terrible.
I know it's hard for small children to remember that they need to ask if they want to play with something that belongs to someone else.
But it's equally as hard for them to understand that the other child will (probably) give it back when they are finished with it, especially if they have taken it without asking.
The OP says that the boy who owned the bucket became upset and she had to intervene, so it's quite clear that her son wasn't giving it back right away. She even says in her first post that "The grandma came over at the exact time my DS was (finally) giving back the bucket..."
If the grandmother was sounding exasperated and sarcastic it was probably because it took two adults to get involved before the OP's son finally gave back someone else's property.
And the OP sounds quite sarcastic herself when she says of the little boy that he "ran off and told his grandma that a nasty monster had 'stolen' his bucket." Did he really say "nasty monster" OP?
And then she chose to come onto a forum and call everyone else shit for not teaching their children to share when what she really means is they should be teaching their children to not complain when their things are taken by her son others.
If children are too young to remember to ask if they can use something they are also too young to remain unaffected when someone takes something of theirs without asking.
There is a world of difference between the baby who picked up a cup that floated past him (that mother was way OTT by the way when she packed everything up) and a toddler taking something out of another child's hands. What happened with the OP and her son is somewhere in the middle of the two.
But the right response in all three cases is to hand back the toy to the child who owns it or was playing with it (in the case of toys at playgroup etc) and depending on the age of your child you then either distract your own baby with something else or you explain to your toddler/child that "X was playing with/owns that. Why don't you play with this instead or ask X if they will let you join in with their game or take a turn when they have finished?"
I don't expect children to be perfect and understand all this at age three. But the adults should and the OP is being very cavalier in her opinions that a child's belongings are less valuable to them than an adults (probably more expensive) belongings and should therefore be available to all. Children put a value on their things that has nothing to do with how much money they cost. And she's quite rude in her assumption that any child who objects to his toy being taken has shit parents.