"Animal flesh and fats are far more difficult to digest for a sick person than vegetables and fruits".
I have to disagree. In some cases, especially when the gut lining is damaged and inflamed, animal flesh and especially fats are the only foods that a person can eat. The very thing that animal products has no fiber makes it possibly as a recovery healing food for people with damaged GI tracts.
"Most sick people are low on stomach acid, and animal proteins require a lot of it for proper digestion"
You would agree that there is a huge difference between chewing a rubbery medium rare beef steak and sipping a rich chicken broth, and eating a chicken leg that has been boiled for 5 hours? Fish, seafood, chicken, and turkey are easy to digest, especially when well cooked (boiled) and can be digested by people even with low stomach acid.
Red meat is hard to digest and requires a lot of stomach acid. You don't have to eat only red meat in order to get your minerals and proteins. You can eat it when you have sufficient amount of stomach acid when you have recovered. Chicken liver can supply you as much or even more nutrients.
Stomach acid is easily replenished with HCl Betaine, raw sauerkraut juice, lemon juice and you need to supplement Iodine in order for production of stomach acid.
"Also, fiber IS essential to human health. Our friendly flora feeds on fiber mainly, and it is well known that 80% of the immune system is located in the gut. A healthy gut means basically a healthy body".
Fiber is not essential. Eskimos historically lived without any fiber and are still doing much better than modern Western population. Nordic people (Norway, Finland, Sweden, Faroe Islands)live on very little fiber. People who have historically lived in prairies (steppes) have lived on meat and fermeneted dairy mainly and teas made with fat (Mongolia).
Gut bacteria live on whatever real food you can give them and are adaptable to any diet as humans live in various conditions.
Fiber can be damaging to gut lining of the GI tract and in case of digestive issues should be the last thing to eat.
Fruits and veggies also have anti-nutrients in them as a means of self-defense. Just like animals can run to save their life, plants have evolutionary developed phytates, lectins, and gluten to survive. They can only be eaten (especially raw) when a person has no digestive issues.
Modern culture is barbaric in the way how we eat plant foods. Fruits have to be peeled and cored, nuts have to be soaked, beans and grains have to soaked, fermented or even sprouted before cooking to eliminate anti-nutrients. Did you know that almond can only be eaten soaked and peeled as they not only have phytates, but also cyanide compounds in their skins.
"Fiber also binds to bile acids, preventing its reabsorption".
That's the whole problem here. You need to look into Anatomy and Physiology. You don't want to prevent re-absorption of the bile acids (unless you are doing a liver cleanse). Re-absorbing bile acid is a normal healthy process in our digestion. Body recycles everything, including blood, tissues, etc. Bile acid are precious and contain vitamins A, D, K, E and lots of other useful components and we do reabsorb them because these vitamins are precious and are not easy to get from diet. They can only be replenished by animal sources of these vitamins. Once you lose them, you are in trouble. Bile production gets compromised. It takes months of eating butter and ghee and drinking raw egg yolks to build bile stores. It's no joke, you surely do want your bile to be reabsorbed.