A lot of people will attach a morality to their belief structure to basically validate their personal opinions. So it’s not a difference of opinion you are immoral if you don’t eat how I eat because I’m choosing the morally good diet. It’s why it’s hard to have disagreeing discourse these days as people have formed their identity around their beliefs and their beliefs are justified by a contrived moral framework so there can’t be a disagreement as this would be both a personal attack on their identity as well as a moral attack and admission of moral failure and who would listen to the opinion of an immoral person

This is an abstraction of a phenomenon that’s been happening in increasing amounts over the last couple decades and the sperging vegan is a very amusing example of this