The problem with your statements and perception here- You are assuming every runner is "doing it right" when in fact most of them are doing it wrong.Everything in moderation.
I run. I have run marathons. I have never
not even once felt a twinge of pain in my knees. Never lost a toenail.
Why? Because I crosstrain.
While I was marathon training last year, I was more focused on running, but I swim 5 days per week, ride my bike 2-4 and run 2-4 days.
If you balance out your fitness, you wont have problems.
So- "Runners = retards" is not true.
Runners that are stupid about running? Yes... maybe so.