Attributing colon cancer to meat is, it turns out, complete bullshit, just like most other nonsense anti-meat fear-mongering (uric acid, cholesterol, etc.).
Before I became vegetarian I read as many papers as I could about why meat is good or bad for you.
Unfortunately a lot of papers don't provide very good data regarding what kind of meat is being eaten. At least, not in what I've read; I'd love to see something better.
Some very specifically included processed meats which, to me, invalidates the study as a study about meat. Processed meats are a completely different beast. On those grounds a significant number of studies I've read are hard to take seriously.
This could be a reason people are calling it bullshit.
I'd love to see a study involving conscientious meat eating habits in which people eat mostly vegetables, some whole meats, and otherwise avoid processed foods. This is how I'd want to eat if I ate meat, but it's rare to see balanced studies.
This does, however, make some sense: most people eat processed foods where these studies are done, so they're relevant to a broader part of the population.
I have the same experience when apparently anti-vegan results/studies appear on HN. Usually the headline is a million miles from what the study could claim to show. It would be nice to actually see this paper.
This was the last time I looked at one of these claims: https://news.ycombinator.com/item?id=23661158 (Article claimed 25% of vegans have low blood iron, and the study involved ..10 vegans.)