I believe veganism is a mental illness therefore I double my meat consumption for every vegan I meet
I assume you don't know much about veganism. Are you aware that it's not a mental disorder?
No I don't know much about veganism, how is it not a mental disorder?
Veganism is a lifestyle and you are being incredibly rude by treating someone different as you as mentally ill. It gives a bad name to veganism and you are diminishing the struggles of the mentally ill.
Why do I care about those people when I can eat what I want?  It is none of their business,
You do not have to take part,  Just because you do not agree with their choices does not mean that they have a mental illness.   You should focus on positive things not related to diet that you may have in common with vegans,