You don't need martial arts for blind people, they won't see you coming with that cricket bat.
Anyways, point in case, I'm not comfortable suggesting blind people have a wish to inflict damage on someone if that might mean jeopardising innocent people and particularly those that might be trying to assist them. And someone will hopefully intercept someone obviously wailing on the disabled. At least I know I would attempt to do so. Last thing I want to have to deal with is a blind person trying to kick me for my troubles, or having to explain to police officers that a blind person struck me while attempting to help them before a mugger ran off.
I think the best self defence for the blind is social, rather than proactive. As in... *they're fucking blind*. People should have sone sensibilities concerning how fucking awful and cowardly that is. A blind person acting aggresively is more likely to get that aforementioned stick to the back of their head.
Which is hard enough to see coming when you do have your senses.
Let's be realistic here. Beating up the infirm, blind and paralyzed is about as low as you can get for physical assault. If the bar is already so low that a thug has so little a spine to limbo under that standard chances are they won't be above striking you when you have no means of reprisal.
Basicslly the only people a blind combatant is going to be hurting is the people trying to assist them.
Being blind sucks.