[simonw]

"I don't see much difference between killing chicks after them being born, or stopping them from being born in the first place."

I do. One of those involves a (presumably painful) death of a conscious animal. The other does not.

[Concrete3286]

The other option - a living female chick - also ends in the premature death of a conscious animal, additionally after a (presumably painful) life. Does it not?

[simonw]

Sure. That doesn't mean that there is no difference between not having a male chick being born compared to killing it directly after it has been sexed.