I am not sure about disabled people getting "ample space". On many planes, the only seats with additional leg room are emergency exit rows, and disabled people are not allowed to sit there (by law).
If it is such an issue for him (and at 6'11" it must be) then pay for the seats.
Anyway, why shouldn't airlines charge for seats which are regarded as "premium"? After all, every passenger would like extra leg room, but how many are prepared to pay for it? The more you want or need it, the more likely you are to pay the price. Cough up and stop moaning!
It's only on budget airlines that this appllies - full service carriers don't usually charge.
And I bet it's your husband that is in front of me at every gig and cinema I've ever been to. ;-)