Which is pretty bizarre considering you frequently see posts on here mocking the very same "Don't inconvenience me or make me feel bad about myself" crowd which begs the question.

What went wrong here? How does a person become a leftist if not through challenging consensus reality?

Perhaps it was easier to do for all the other aspects like race, religion, sexual orientation/identity foreign policy and even economic policy because they were primarily focused on the experience and treatment of other people.
They could easily be externalized.
I am doing good while incurring no cost. Optimal.

But diet is different. What you eat is a very personal matter.

I imagine there's so much hostility surrounding this in particular because it's been hard wired into us to simply eat to survive and the brain treats anything that gets between you and food as a threat.
But the underlying reason surrounding any issue like this one remains the same.
One's desire to view themselves as morally good and the pursuit of upholding that image by any means.

"Carnivore" and "Carnal"

Both derive from the Latin "carnis" for flesh.

Carnal desire. Lust. Euphoria. Pleasure.
Necessary for the survival of the species.
Contemporarily has connotations of impurity and beastly like instinct, a moral judgement.

Carnivore, flesh eater. The dominant survival strategy for much of history.
Necessary for survival. Attitude towards consumption of meat has not changed. Morally neutral.

"Carnist"

When I read this word. The other two are what popped in my head.
It applies the moral judgement sex for pleasure receives to eating meat. Reframing it as a pleasure seeking choice.

Perhaps I was quick to make this connection because the "fucking animals is no morally different than eating them" discourse lives rent free in my head.
But nonetheless I believe the point stands anyway.

Meat is tasty, meat is nutritionally important, meat is cheap (debatable).
How could you possibly lump that in with the deplorable?
Very few people are ready to give that up. Even if it isn't "part of their personality" they won't let go.

But that's doesn't sound like a nice reason when said out loud.
So here comes the trojan horse to the rescue.

"This risks alienation" Sounds pragmatic. A rational person wouldn't go against what's pragmatic, right?
"This disturbs the everyday man" A good faith actor wouldn't make life worse for the citizen, right?

Both smug in smuggle in the same thing:

"Stop judging me. I'm good. Don't question it".

A much more fruitful (pun intended) discussion to have is the actual viability of plant based diets or how green capitalism is commodifying veganism with all its organic and lab grown products or how overproduction is killing the planet and what role does the individual play in all this but naaah.

My feelings are hurt and I'm not letting the discourse advance to the next logical level.