Isn't it lovely when someone has the audacity to complain about rules and fairness when they don't know any of the rules in the first place? It seems like this mom is under the impression that martial arts tournaments are about fights to the death, and making it so your opponent can never walk again. Which is what led to her freak-out when noticing OP putting on a very medically necessary knee brace.
Despite the fact that it's fine to have a knee brace, officials knew about it, and kicks to the knee are illegal anyway, this mom wasn't having it. Apparently she was under the assumption that it was protection against a competitor stomping the everloving meniscus out of her knee, which is again, illegal, and not that it's being used so this competitor can actually stand. Thanks lady, for making everything more complicated for no reason.
For an intriguing tale of leg-based drama, here's the guy who tried bullying a woman out of a disabled parking spot, so she showed him the stump.