Morality is entirely esoteric...
Plato’s Euthyphro is a great illustration. Socrates advances the argument to Euthyphro that, piety to the gods, who all want conflicting devotions and/or actions from humans, is impossible. (Socrates exposed the pagan esoteric sophistry.)
Likewise, morals are such a construction of idols used by the Left as a rationale for them to demand compliance to their wishes in politics, which most often are a skewed mess of fallacies in logic. Morals are a deceptive replacement for the avoidance of sin.
An atheist who says I am immoral is no different than a rabbi or preacher saying I am a sinner. They just slap a new label on it hoping nobody will notice - - they replace the idea of "avoiding sin" with "morals."
Try an experiment. The next time you are confronted by a neo-pagan, New Age animal rights eco-fascist who claims humans were not "designed" or "meant" to eat animal flesh, ask them about the origin of their creationist philosophy. Inherent in such a claim is the idea that there is a "designer" or some divinity of "meaning" in human existence. Would they apply this to abortion, embryonic stem cells, or homosexuality? No?
Now that would be fun. Of course I do know meat-eating pagans who think Greenpeace is full of it -- I have little tolerance for the kind you describe. Actually, where do some of the modern pagans get this vegetarianism? I'm pretty sure all of the pagans of old were meat eaters, too busy living to worry about whether they should be eating animals.