IMHO, a blind person would be able to hear CC commands, and feel their way to an exit, with the best of the sighted people, particularly if the cabin is full of smoke.
From the information given, Ryanair fulfilled their Ts&Cs, but perhaps should have handled the incident more discretely at the "front-end".
Blind friends of mine are very proud of their independence, and would be mortified to think people consider them as "disabled"