"Hitler was a vegetarian. You aren't like Hitler, are you?" is a fair reason to run a garbage-collection pass over your beliefs if you're vegetarian, checking your reasons for it -- but invalid argument against claims that vegetarian diets are healthy. It sounds like mid-century historians collectively made the latter mistake.

That's an attempt at dismissing a priori the issues outlined in the GP, completely avoiding addressing them. These are very serious issues with very serious consequences; dismissing them won't change the outcomes.

Assuming you also don't want these horrible outcomes, it doesn't make sense to dismiss the risk. The people who advocate dismissing it are the ones who don't care about or seek those outcomes and are trying to remove obstacles.