So... if you're not acknowledging where the meat comes from, that's bad
But if you are acknowledging it, it's bad as well?
Many people who eat meat do that not while lying to themselves about where it comes from as many vegetarians/vegans assume. They just legitimately do not feel bad for the animals they eat. Just as so many of us don't feel bad about the clothes they wear or the smartphone batteries they use.
The world is full of abuse, suffering and other such bullshit. You can't feel bad about all of it, or you'd go insane because you can't escape it. Besides, the brain just numbs itself at a certain pöint. So you need to allocate your compassion to a few of the sufferings you know of. Many go with animals for that. Many don't.
So the question isn't why the person eating meat is heartless, the question is what kind of pity the person not eating meat left out for it.
That's how my mind processes the whole thing.