At this point, so many silly complaints have been lodged over absolutely nothing that I can't tell if this is a legitimate concern or satire.
Well the complaint is either that you can kill kids in this game, or that you can not kill all kids in this game. Honestly this should be out of the question totally, but the OP is correct that it is at least a double standard, especially when your game is otherwise trying to be very inclusive.
It is also not consistent with the current lore, as in SoD you at least can have a goblin follower, who is true neutral and a rather gentle soul, too. It is said that she is this way, because of her maturity, so she might be an outlier, however does mean that Goblins are not absolute evil. This does not matter either, as the morals of the story are a reflection of today's morals. And in today's morals killing of infants or kids is universally condemned, especially deliberate. Going against that code of conduct is so rare, that the need of representation through implementation of it is inherently worthless.
Because it couldn't be something as simple as a minor oversight on flagging NPCs or have something to do with alignment, right? This is clearly some agenda that we need to quell before it gets out of hand.
Sure, could be, but even then the OP is correct in calling this out as a bug. Still I suppose you are talking about Tiefling kids not being attackable and not Goblin kids being attackable. The problem with having that option is that, while the game wanting to represent contemporary moral standards and also include being able to open a wide variety of choices, they do not offer the corresponding consequences. Does the killing of the Gobbo kids remove the option to side with the goblin camp? It should. It should also have several other consequences like companions leaving, quest givers not giving quests anymore, certain factions or NPCs being hostile on sight, restricting certain traders, increase trading prices and so forth. So it would reflect the consequences of the real world, they are trying to represent in a fantasy setting.