Who says rock musicians are fine? I bet most self medicate for their symptoms.

<But the studies on headbanging are disputed and nobody has an unquestionable answer.>

Those that dispute the damage caused by head banging are no different that the neurologists and other MD's who believe you can not suffer prolonged symptoms/damage from a concussion unless you lost consciousness.

Jumping on a tramp in many cases allows the body to absorb much of the impact. So does jogging. The spine has a natural S shaped cure as a form of a spring to absorb impacts from the foot plant. The padding in modern running shoes also absorbs much of the impact forces.

Regarding your aversion to seeing head banging, I have the same reaction to seeing any form of quick head movement. People are often sensitive to seeing others involved in activities that will make you uncomfortable if they happened to you.

Some of these sensitivities are part of the PTSD spectrum of symptoms. It is like a flashback.