If you take a detailed look at all land-based foods you will find one similarity, they are all bad for you in one form or fashion. Even the fad so called "superfoods" such as kale, eggs & coconut oil. Out of all the millions of land-based plants about only 20,000 of them are edible and even those are still harmful to humans in other ways. Vegetables have natural self-defense chemicals that are used to protect against predators like humans.
Animals are all high in saturated fats, have hormones that too are too close to human hormones so they have an ill effect on us. They also contain parasites and microbes that cause us to be ill.
On the other hand, out of all the sea vegetables, most all of them are not only nonpoisonous to us but highly nutritious. They also contain the necessary elements such as iodine that land plants do not possess. As well, fish has the perfect kind of saturated fats and Omega 3's without all the harmful hormones, parasites, and microorganisms. Have you ever wondered why you can eat fish raw at a sushi restaurant but you wouldn't even think about eating chicken, beef or pork raw?
Yes, there are good things in land-based foods but there are bad things as well. Why consume something that is both good and bad when you can choose to consume something that is only good and has no known negative qualities.
When you connect all the dots it becomes very clear as to what we should be eating and what we shouldn't.