Fruit isn't healthy for any human, but the extent at which it causes damage depends on the person. Some can tolerate it fairly well, and don't find out it was the cause of their chronic issues until they remove it. Only one way to find out if they're the culprit - try carnivore for 90 days!

Ray Peat followers are not serious people

The reason why your vegan friend is constantly locked in a mental/hormonal battle with their body is because their brain is nutrient-deficient. The brain is made of FAT, so it needs FAT. It's that simple. You're never going to fix these problems as long as your brain is starving.