shouldn't be the one who would willingly harm those goblin kids in a deadly way
Why not?
would he decide to kill that owlbear cub?
Most likely, yes ...
Owlbears are Monstrosities ... meaning Druids often kills them on sight, since the break natural order.

And since druid are able to talk to an owlbear
Basicaly they are not ...
But Larian decided to break the rule here, to allow us this, bcs they thought its fun option.