I'm not familiar with these studies, but I suspect you are misinformed. I'm happy to read them if you have links.

The largest, longest, best designed research shows vegans living longer and heavy meat eaters having high levels of atherosclerosis.

It is not an argument, I'm not logically deducing anything. It is the results of the biggest and best studies.

Even the nutritional researchers tend to live to 100 or more, probably because they follow the results of what they study. Ancel Keys lived to 100, Dame Harriette Chick to 102, Dr John Sharffenberg is 99 or 100 now, whereas Atkins died in his 70s, Pennington (who Atkins based his diet on) died at 56, Charles Poliquin died at 57, etc. There are lots of long-lived vegetarians, seventh day adventists, Okinawans, nutrition researchers, etc. The studies on longevity show what they eat, and it's usually close to vegan. But the best predictor is actually conscionciousness, then income level (diet seems to follow from both of those -- conscientious enough to actually rigorously do the right diet, and rich enough to afford all those fresh fruits and vegetables).