Allowing An Animal's Existence is not Justification for Torture

A common argument used by meat eaters:

Cattle wouldn't exist in their millions unless they were bred for meat and leather. In fact, they have no niche left in the "natural" world. ARE YOU ABSOLUTELY SURE that cattle would choose not to exist at all (as would be the case in a Vegan world) over existing for a while, and then being slaughtered???

A reply by Lucy Tancredi:

Trust me - no question you can ask someone who has been vegetarian for at least a couple years has not already been asked him or her hundreds of times. Yes, I've considered that question.

If I decided I wanted to eat human flesh, and gave birth to a child for that express purpose, and kept it for its whole life in a crate barely bigger than its own body (as is done to veal calves), would I be justified because at least I gave it life?

I don't pretend to know what a calf would want, but I personally would rather not live than live a life of torture. Obviously some food animals have better lives than others (e.g. dairy cows have much better lives than veal calves, chickens, or pigs in factory farms). But some really do live lives that aren't (in my opinion) worth living - penned up in darkness their entire life, unable to socialize with others of their species. Would you want to live your entire life in solitary confinement?