And a second is "how much better or worse is this animals life compared to a similar animal in the wild?"
My personal opinion is anything that doesn't meet the first benchmark is evil. Anything that is between the too is in a gray area. And anything past the second I don't need to feel too concerned about, or I'd describe it as ethical husbandry.
It's clear that there are plenty of chickens whose lives are soo terrible that don't meet the first benchmark and their extinction would be preferable to their current experience