They don't fight in "cage matches", sporto. The kids (not the adults) fight on mats, just like they do in every other combat sport. And they wear protective gear (lots of it), and everything is VERY closely supervised, just like ever other sanctioned combat sport event. I don't have any scientific data, but to me it's a ton safer than youth football because your kid is never going to be facing someone who is significantly bigger, stronger, or more skilled because the rules simply don't allow it.
But let's keep pushing the stereotype that the sport is about little kids "pounding the hell outta each other", as if there's even a grain of truth to it.