I agree with you. But you know what? I'll probably force my kids to do gymnastics (unless they seriously hate it).
My mother took me to gymnastics because she began noticing that although I was progressing academically, I was displaying aberrant behaviours. She thought that gymnastics would teach me discipline. And it did. I doubt that I'd be where I am today if I hadn't gone to gymnastics. And there are some genetic defects in my paternal line that I'm really not keen on passing on to my future kids.
But yes, gymnastics is dangerous. And it's not just the inherent danger of the sport - you also find that there are some pretty sadistic coaches out there. I've had coaches push me until I collapse; I've had coaches physically sit on me to force me into an "over split" (a split with one leg on a crash mat and the other extended on the ground behind you. It hurts like a motherfucker even without some asshole sitting on you); I've had coaches refuse to let me cease training whilst recovering from injuries as severe as torn ligaments and concussions. I've had coaches scream at me; I've had coaches ignore me for entire sessions (that's a good method of control for an impressionable young gymnast: when your coach suddenly stops paying attention to you, you start to wonder if they've given up hope and that's when you end up on the beam doing back flips without a spot, despite having never completed a back flip on the beam before). I once had a coach tell me that if I wanted to get into the Australian Institute of Sports I would do well to allow their doctor to inject me with a "supplement" that would help me train faster and for longer. I was fourteen and yes, I did and yes, I trained for longer and faster. And gymnastics parents? They're even worse.
Gymnastics is also massively rewarding though. I would compare the natural high you get completing a flyaway from the high bar to the high you get from a line of cocaine. You become fit and strong and even now, after fifteen years of not training I'm already re-adapting to the demands of the sport. My resting pulse has never been more than 40 beats per minute; my blood pressure is 90/60 (which sounds low but is apparently normal for an athlete) and the last time I tried to request a glass of wine on a flight the stewardess told me that I was too young to drink! The strict dietary requirements probably play a part in that (though it is true that some gymnasts are starved, I was never starved: I just ate a lot of vegetables and consumed protein drinks, plus three litres of water a day and two cups of spirulina). But the long term dangers - amenorrhoea, osteoporosis, premature arthritis... there are certainly extremely concerning consequences. I can tell you that the rumours that gymnasts are given drugs to delay puberty are probably false - the sport itself does that. I didn't go through puberty until after I was forced to quit gymnastics, and that's perfectly normal for women in that sport.
I benefited greatly from gymnastics and I still love the sport but only the strongest survive. Even that's not entirely true - a strong person can still be broken by this torturous sport when the stressors pile on. There are benefits to enrolling your children in gymnastics, but those have to be weighed against the possibility that any one of the terrible things I've seen in that sport could happen to your kids.
EDIT: I loved your old avatar and this one's pretty cool too, but why the change?