Charlie, don’t be dense. Yes, it is very wrong to live by a moral code which opposes the morals of the Torah. And yes, moral vegetarianism opposes the morals of the Torah.
The fact that it happens to do so by amplifying out of proportion other Torah morals is inconsequential.
Shaul thought he was doing a mitzva by saving the animals of Amalek to bring as karbonas. Hashem said, I don’t need your korbanos, I need you to do the ratzon Hashem.