To be honest Goblins are despicable creature by nature. Opportunist and most of the time even coward. Their Strenght comes with the number and they often attack in pack on easy target. During my playtrough i was put in between a choice to leave the Goblin children run and allow them to warn all the camp or get rid of them then deal with the adult. I chose the latter with no regrets. Goblins are evil. When you first meet the goblin childrens they not only playing with a corpse they also threaten you. While i dislike absolutely invincible npcs. Childrens are often in videogames.
I won't make a comparsion between Tiefling child and Goblin child. Tiefling are born and often victim of a lot of prejudice due to their fiendish heritage but not all of them end to be evil.
Goblin on the other hand are a despicable evil race. So. The only good goblin is a dead goblin.
So you're telling me it's okay to kill a cute little scamp like this,