dont want to over generalise but vegans seem to be the best people out there to be friends with for me. if they care for animals, not wanting them to suffer a lifetime just for a short time of our pleasure, they most likely wont treat you bad as friend. there is no valid statement on why people shouldn't become vegan, we have supplies to vitamin b6 and b12. studies have shown the blood of people on plant based diets are far more superior when it comes to eliminating cancer cells, compared to regular dairy and meat consumerists(source:what the health, documentary). dairy products increase chances for developing breast and prostate cancer.
there are many good reasons on why its better to go vegan or at least eat less animal products, the biggest ones are ethical and health reasons.
sadly, as with any other business, there are people who have determined their whole life in producing meat and dairy products who don't want to give up all their efforts, sharing lies and trying to influence us with their lobbyism .
i like eating meat, at times i do but very rarely, i do my vitamin b's and maybe 1-3 times a month i afford myself good, cruelty free, organic meat without feeling guilty:3