"Vegan to herd of cows: Sorry but you should never have experienced life at all, even for the brief time you are being fattened up."
Er, honestly? I'm not vegan (nor vegetarian), but this sort of reasoning is on pretty dubious ground from a purely logical point of view.
Does this mean (for example) that by not attempting to get a woman pregnant at every possible opportunity that I'm depriving those nonexistent children of life? Would it matter that they might have a pretty rotten life if that was better than "never having experienced life at all"?
Or (more in line with your reasoning), does this mean that anyone against reckless procreation like this is effectively saying to the children of such irresponsible people that they shouldn't have existed at all?
It's a philosophical can of worms (#) being misused by yourself as a form of smartass quasi-moral blackmail.
(#) I've no idea if the can of worms is vegan-friendly or not. Are they still meant to be alive when you open the can? What is their intended purpose? Are we intended to eat or exploit them? Do Heinz do a curry flavour version too?