Read up on the McGovern commision
In January 1977, after having held hearings on the national diet, the McGovern committee issued a new set of nutritional guidelines for Americans that sought to combat leading killer conditions such as heart disease, certain cancers, stroke, high blood pressure, obesity, diabetes, and arteriosclerosis. Titled Dietary Goals for the United States, but also known as the "McGovern Report", they suggested that Americans eat less fat, less cholesterol, less refined and processed sugars, and more complex carbohydrates and fiber. (Indeed, it was the McGovern report that first used the term complex carbohydrate, denoting "fruit, vegetables and whole-grains".) The recommended way of accomplishing this was to eat more fruits, vegetables, and whole grains, and less high-fat meat, egg, and dairy products. While many public health officials had said all of this for some time, the committee's issuance of the guidelines gave it higher public profile.
The committee's "eat less" recommendations triggered strong negative reactions from the cattle, dairy, egg, and sugar industries, including from McGovern's home state. The American Medical Association protested as well, reflecting its long-espoused belief that people should see their doctor for individual advice rather than follow guidance for the public as a whole. Some scientists also thought the committee's conclusions needed further expert review. Others felt that the job of promulgating recommendations belonged to the Food and Nutrition Board of the National Research Council. Under heavy pressure, the committee held further hearings, and issued a revised set of guidelines in late 1977 which adjusted some of the advice regarding salt and cholesterol and watered down the wording regarding meat consumption.
This isn't about this one study. This is about a long history of data showing meat is bad for you. And a long history of industry getting their way by throwing political tantrums.