Earlier quoted context omitted.
I'm gonna go ahead and say that if something is bad enough to kill someone who is somewhat weakened, that doesn't make it fine for folks who aren't weakened. This is an extreme diet and even if it doesn't kill you, it's ridiculous to think it will do you no harm. If you're at risk of death from taking antibiotics because you only eat fruit, the problem isn't the antibiotics.
only eating fruit is not an extreme diet at all, especially if you're consuming the right number of calories. what makes you think it's extreme?
Modern fruit has been genetically engineered (via selective breeding or other means) to be much more sweet than their wild counterparts, and hence contains much more sugar.
Surviving on wild fruit is probably not really that pleasant since most of them don't really taste that great.
PS: generally fruit have little protein, so you might also want to find some extra sources of protein too.