A demand for the average American to eat more meat would have to explain, as a baseline, why our already positive trend in meat consumption isn't yielding positive outcomes. There are potential explanations (you could argue increased processing offsets the purported benefits, for example), but those are left unstated by the website.
[1]: https://www.agweb.com/opinion/drivers-u-s-capita-meat-consum...
[2]: https://ers.usda.gov/data-products/chart-gallery/chart-detai...
You need to go to much more recent times to get worsening results/predictions.
There was no such observation, just claim going contra observed data. The period you picked does correlate meat consumption going up with health getting better.
You said that meat consumption went up for last century. Then you claimed that "our already positive trend in meat consumption isn't yielding positive outcomes" - except that majority of that period did yielded positive outcomes.