> I take this as further evidence that exercise is dangerous.

What does this even mean? Whatever we call exercise is an arbitrary threshold. Humans, unless they live their life bound to a chair, move about, in different degrees, and anything more than walking we can call exercise.

Humans have evolved to cross this exercise threshold multiple times a day simply to survive (who's gonna catch that running antelope?), so how can moderate movement for more than 5 minutes be dangerous?

It might be because of your set of physical issues, but it's not a rule.