Observational studies have no validity. For example take John. John doesn't really care about his health. He eats a lot of red meat and saturated fat (which we are told is bad for you) or whatever he feels like, including a high processed carb, high sugar diet. He also doesn't exercise, he drinks and he smokes. He is also overweight due to his lifestyle choices. Not surprisingly, John has a lot of health issues.
Then take Jack. Jack cares about his health, so he doesn't eat a lot of red meat and saturated fats, and eats mostly white meat like chicken and fish, because he is told they are good for him. He exercises regularly, doesn't smoke and doesn't drink. Not surprisingly, Jack doesn't have many health issues.
A group of researchers ask Jack and John, and many others to fill out a questionnaire to see if high consumption of red meat and saturated fat is related to health problems. They conclude that people who eat red meat and saturated fats are more likely to be unhealthy.
At no point did the researchers ask what other foods they ate, how often they exercised, if they drank or smoked heavily, and if they were overweight.
What i have said describes a vast majority of "research" done on saturated fats and red meat. Correlation does not equate to causation.