What do you think a daily changing shift schedule (Late - Early - Late, etc.) will do to your health over the course of 35+ years ?
Not to mention the same amount of inactivity as a battery hen. Everytime I went to my physio' for some lower back massage they kept telling me to be more active every day and spend not too much time just sitting still. Even a long distance lorry driver gets a decent break and some activity every shift. 40hrs per week of inactivity is inhumane.
Considering many modern pilot are trained monkeys then animal cruelty issues might be relevant.