If the race eats people in general, they are monsters in my book.
If SOME don't eat people, those are rare offshoots of a monster race.
Goblins eat people. Tieflings don't. Therefore, I would consider goblins monsters and tieflings not.
That said, I don't like killing the children of either.
That said, if I'm in a hostile monster camp, and their kids are going to warn their elders to come kill me, I must kill them or I will likely die. Likewise, if tiefling children are going to turn an entire grove full of tieflings against me, to survive, I should probably kill them.
They bedevil travelers. They harry frontier villages and towns. They swell the ranks of their more ambitious and stronger kin. Rare is the individual who will shed a tear for their deaths.
