They resemble a religious cult in the sense that they believe their diets can heal anyone from any type of illness and grant you superpowers. Advocates say we must go back to primal eating habits, for a diet comprising 70-80% fat, mostly saturated. However, this contradicts historical evidence from hunter-gatherer societies, which consumed an omnivorous diet and leaner cuts from wild game meat, unlike their recommendation of daily butter bars and bacon.
They blame carbohydrates as the root of all evil and ignore the fact that we're eating more calories than ever and that we went from doing a lot of physical activity to being inactive due to sedentary jobs and sedentary forms of entertainment.
Most of their gurus are snake-oil salesmen following the trend to make videos or wanting to sell you supplements like a panacea.
I have a sister and friend who got converted to keto dieting telling everyone how they will develop diabetes and die if they eat a bit of rice, which is ridiculous.