I can't reply to every point that everyone makes -- I've been commenting on this thread for quite a while now. But I'll do my best!
In fact, I am so convinced that the carnivore diet would be a panacea for the world if we would just do it at scale that I am thinking of writing a book about it, which I would title "The Carnivore Panacea".
The association between red meat and colon cancer is "an association". Note that in nutrition science it is extraordinarily hard to demonstrate "causation" rather than "an association" because to demonstrate causation you would need the kind of double blind, placebo-controlled trials that are basically impossible to administer in this field.
Most nutrition science relies on people remembering what they ate last month, or feeding people in a controlled setting for a few days or weeks rather than the few months or years that would be necessary.
So, to put it bluntly, I am absolutely certain that eating red meat does not cause colon cancer -- but I am aware that this is a major talking point that has caught hold in the culture.
As for the "suffering" that eating meat causes, it is nothing in comparison to the suffering that eating plants causes, so I think eating meat wins easily on that count.
Note that some people think that if there are only plants on the plate of food that they are eating from, then this means that no animals were harmed to bring them that plate of food. For these people it is just a matter of pointing out the ecological costs associated with agriculture:
* the ten-thousand-acre mono-crop farms the destroy habitats,
* the massive quantities of insecticides that kill all the insects
* the secondary effect on the bird population that has plummeted due to the insecticide use
* the transportation costs (meat is more likely to be local than plant-based food)
* the impact on the health care sector (a major contributor to global warming) from the obesity, cancer, diabetes, and heart disease
All of the above can all be summed up by picturing the vultures that circle behind those combines on those massive mono-crop farms -- vultures because they can devour all the baby deer and little foxes and ground-nesting birds and little mice that live in the fields and get chewed up by the combine -- because when the harvest time comes, death comes with it.