Not all beliefs are good. Veganism seems to minimize suffering for a group of life on this planet that has traditionally been at the whims of humans.
But as another commenter pointed out, people's egos can't usually take the claims that they are making bad choices and should change. This kind of pressure shows up in exercise, for example.
Animals dying don't care about egos though. On the one hand, entire beings seize to exist, while on the other the top predator remains to exist and satiate their taste buds with a steak or pork chop.
If you are concerned about moral behavior in this world, then you can't not extend that consideration to animals. If you can't, then you're morally inconsistent.