Are blind people allowed to ride bikes on the road? Are blind people allowed to drive?
Hearing what's coming up behind you is really important. Especially on a bike when you have no mirrors and the slightest graze will send you into a tree.
I can see what you're saying Helios, but I doubt you'd get much traction for a case. Lots of deaf people are very handicapable and riding a bicycle is perfectly possible and safe even when profoundly deaf.