Here is a quote
Men and women with higher intake of red meat were less likely to be physically active and were more likely to be current smokers, to drink alcohol, and to have a higher body mass index (Table 1). In addition, a higher red meat intake was associated with a higher intake of total energy but lower intakes of whole grains, fruits, and vegetables.
Here's a bit from earlier on in the methodology section.
We analyzed data from 2 prospective cohort studies: the HPFS (initiated in 1986, n = 51 529 men aged 40-75 years) and the NHS (started in 1976, n = 121 700 women aged 30-55 years). Detailed descriptions of the cohorts are provided elsewhere.7-8 Questionnaires were administered biennially to collect and update medical, lifestyle, and other health-related information, and the follow-up rates exceeded 90% in each 2-year cycle for both cohorts.
So basically what they are doing, is picking a couple studies, from who knows what all available data. Then they go by questionnaires. They even admit to all the other things associated with the red meat, as if eating red meat makes people do that, rather than people who do that don't underestimate something viewed as "unhealthy" at the time of the studies.
They also fail to separate all the other variables involved here. So how do we know what caused what? Not to mention the whole thing was presupposition from the beginning. They chose that variable, trying to find those results.
That's not how science works. In science, you make conclusions from the evidence, you separate all variables, you don't assume a relation is causative without evidence, and you don't cherry pick.
If you do all those things, it's pseudoscience.
People all take this seriously because of confirmation bias. So nobody questions, and everyone thinks you're nuts if you do.