Joking aside, you're asking for justifications in the nature of mortality. There are numerous thoughts on the matter, and no single unifying theory of mortality. Many great philosophers have attempted to create their own theories. Socrates, Kant, Bentham. All different ideas, all with holes.
Vegetarianism and veganism have flaws as well. Ignoring the fact that supplements cannot be mass produced in enough levels to allow the entire human race to be on these diets (and even if they could, we have more than enough food for the entire human population and people are still starving in no small part because of the logistics of getting that food to other people) you still have the agricultural shortcomings that all land is not equally fertile. You cannot necessarily grow human consumable crops on grassland, but you can feed grass to livestock for food. Speaking of livestock, much of them are domesticated and cannot survive without human involvement. Will you take care of them? Or is genocide preferable for those species?
How about environmental impacts? In order to increase agriculture for human crops, the rainforests have been cut into. On the extreme end, vegans argue that we should stop beekeeping. The thing that increased the bee population. That's a post in and of itself.
Can I trust you grow and eat your own crops? If not, factory farming kills innumerable field animals while harvesting those crops you eat. I have a garden. Do you? All my vegetables, I grow myself. At least I eat the animals I contribute to killing, rather than letting them rot in a field.
So what else do I do? I cut back on meat so I can spend a little more on meat that I research so I know It's not factory farming. I also give more precedence to other humans than I do animals. I also hate organizations that pretend to care about animals and then kill them because they think domestication is bad.
You dare to say I should justify my decision? Why don't you justify yours?