This is what years of Disney movies gets you. I particularly liked the moment when, if you spare the owlbear cub, it tentatively goes to it's mother's body...and starts eating it.
As a dragon enthusiast myself I can tell you I avoided killing dragons in Dragon Age as much as possible because...dragons are cool...and endangered? Listen my rationalization isn't great but what can I say. So I'm maybe not qualified to speak on the morality of culling the nest.
Like with a lot D&D lore, I've never been too enthusiastic about the dragons they give us, so I never knew that if they went against their inherent alignment it is physically manifested. Very interesting. If that's true of Devils and Fiends too, why doesn't that manifest in Tieflings? I'm always confused when the metaphysical translate into the physical in situations like this. Or doesn't not happen with Devils? That's interesting too.