Why wouldn't a lawyer want to add amusement park injuries to his list of specialities? I know I would want a lawyer if I got injured and a park was at fault! He's just doing his job. The legal system is what it is, for better and for worse.
It's up to the parks to keep their sh*t in order so frivilous lawsuits can't get anywhere (security cameras, detailed investigation reports, witness statements, warning signs posted everywhere, proper documentation, proper maintenance, etc.) in the first place. Lord knows they're not going to stop anytime soon.