>None of the dietary studies that I have seen has provided any conclusive evidence that meat per se is the harmful ingredient
This is innacurate if not simply false; according to the WHO red meat is a class 2 carcinogenic and sausages are class 1 carcinogenic. This leaves only white meat as non cancerogenic
If you look at the data vegan (and vegetarian to a lesser extent) diets over various studies consitently perform better in cardiovascular health and cancer rate (colon in particular) compared to the omnivorous conterpart
Those mentioned by you are very specific kinds of meat, and there were doubts about how healthy they are long before the last century.
There is absolutely no evidence that any data about red meat or sausages also applies to other kinds of meat, e.g. those that have negligible content of myoglobin and saturated fat, like poultry breast or white fish.
I agree with what you said, that almost any study about vegan or vegetarian diets shows positive effects, but it is never clear which are the differences from the comparison diets that really mattered, because the compositional differences between diets were too many and too variable.
The OP is actually talking about the studies that the WHO was using to classify meat as a class 2 carginogen. For meat preserves the evidence is clear and known mechanistically, but for meat in general it's inconclusive at best and badly-designed at worst.