I voted that they should all be killable. I rarely play a truly evil character, but when I do I find it incredibly obnoxious when there are NPCs that are purposefully there to harass my character that the game won't let me retaliate properly against. If the game didn't want me to kill the tiefling children it probably shouldn't make them steal from me and act like condescending little imps that think they can threaten me.
You can get them killed anyway. It just happens off-screen and the game attempts to make you feel bad about it.
The goblin kids are every bit as sapient as the tiefling ones but the game actually makes killing them the optimal strategy. It's a weird double standard. Especially since anyone not well versed in DnD is not going to see an intrinsic difference between child goblins and child devil people.
Ahem. Let me put it this way. I call any creature a monster who:
1. Goes about purposely killing people for fun.
2. Purposely tortures people for fun.
3. Enjoys raiding villages and towns with the sole intent of killing and eating people.
4. Enslaves people and cruelly mistreats said slaves, often eating them when they no longer prove useful or just because they're hungry or just for fun.
I am curious if you'd hold to this view if it were Drow children. After all, the Drow do basically everything on this list save for eating people, and even then they feed you to spiders.
