I was thinking about this, sorry for the long post. TLDR: Finding orc babies is a train trolley dilemma, there is no good answer, just a choice of bad ones.
While I would never set up a scenario like this I do think it came up in a game long ago I played which in part explains my answer above. To me, this is a D&D variation of the trolley dilema (do you allow the trolley to kill 5 people or pull the lever and kill 1 person). It's a no-win situation.
You've been adventuring, hunting a band of orcs that has been attacking local villages. After a tough fight, you killed them all. You then find their lair, and some orc babies. What do you do?
You know a few things.
- There is no way anyone will adopt them. It's been tried in the past, the orcs killed the other children in the orphanage and their caretakers before escaping. Every time, no exceptions.
- If you leave them they will starve to death or be eaten by cave spiders. There's probably a one in a thousand chance of them surviving, the others will die suffering.
- If they do survive they will grow up to be evil monsters. There may be a one in a billion chance that they aren't evil, it hasn't happened yet that anyone is aware of but who knows?
So do you
- Try to take them back, knowing the villagers will kill them to protect their own children.
- Leave them to die, because there's a one in a trillion chance one of them could survive and be the first orc in the history of the world to not be evil. By a large order of magnitude, the result of any orc living would be to allow a monster to live that will slaughter as many innocents as possible.
- Kill them and pray for forgiveness.
To me, this is a no-win situation, the least cruel thing you could do would be to limit their suffering. I made my decision and decided to throw the metaphorical lever. The least evil option left to my character, the most merciful solution, was to kill them and pray for forgiveness.
Is that an "eww" situation? Yes, which is why I would never set up the scenario. But from the perspective of my PC, he was still killing monsters. Just not ones that were an immediate threat.
I understand that in some campaigns, orcs are really just misunderstood noble savages who just want to live peacefully in orc-town and only have evil tendencies because they're in a goth period. I'm assuming the monster manual is followed, and orcs are evil ravaging hordes.
It is a conceit of D&D that there are evil races, something that doesn't apply to the real world so no cheating by saying "I'd adopt them myself and we'd all be one big happy family".
Or let's take an alternate scenario from a sci-fi scenario. You're a specialist accompanying some space marines going to find out what happened to a colony. You suspect the colonists were all killed by xenomorphs, but for plot reasons you go with them. For further plot reasons, you don't nuke it from orbit like you should. After the xenomorphs have killed the marines, you come across the xenomorph queen who appears to be sentient (smart enough to understand an implied threat in any case) and some xenomorphs eggs on the verge of hatching.
Do you
Torch the eggs so they never have a chance to hatch.
Let the eggs hatch because maybe the xenomorphs are just misunderstood noble savages?
I think this latter scenario is closer to base D&D morality. Because the xenormorphs are not humanoid we don't sympathize with them or assume they maybe, might, just possibly be good.