To those of you who are taking swipes at the original poster, I suggest a bit of common sense is applied. At no stage did F3G make disparaging comments about the Disabled pax - he was making what I consider to be quite astute observations.
I have an aunt who has severe debilitating Cerbebral Palsy, and if I were to have her on an aircraft with me I would not even consider sitting her next to someone who was not part of our party.
Its unfortunate that in this case F3G was not able to understand what the nature of the disability was, as some conditions have far greater effects than others. For example I would never dream of seating a person with moderate or stronger Autism next to someone who was not part of the travelling party.
I daresay had there not been a language barrier this situation may not have progressed as far as it did - in any case from a safety point of view had the Disabled pax not been able to do his own seatbelt he should have been sat directly next to the carer anyway.