I think it could be argued that more well-trained athletes (via technology,) especially football players, pose as much or more of a threat to fundamentally altering their sport, than the golf ball and golf club are ruining the game of golf.
But my premise forces us to compare/contrast the athlete with the equipment.
Everyone is keenly aware of the recent suicide of Junior Seau, the huge impending NFL lawsuit, bounty gate, etc...
Football players, via technology I.E. better training, better nutrition, lighter gear, better drugs, are bigger and faster than ever. The collisions are becoming so violent, unsuspecting ball carriers are getting killed.
There have been dramatic changes in football rules over the last decade. You can hardly lay a hand on the QB without getting a flag thrown. The game has become far more passing oriented because defensive backs can hardly lay a glove on receivers anymore.
While it use to be risky going across the middle for fear of Ronnie Lott taking your head off, now we have this ridiculous rule about hitting vulnerable players who don't have the ability to protect themselves. You can't hit anyone anymore, borderline calls are ruining the essence of the game.
Furthermore, studies showed that a majority of NFL injuries came about via the kick off. So, they moved the line from where they kick off and now pretty much every kick off is a touch back. BORING
In conclusion, I say technology, manifest in a bigger, stronger, faster and more dangerous athletes, has fundamentally changed the game of NFL football for the worse.