We don't know the full story here. we don't know how many 'able' people were travelling with the group. And where did they get the maximum 4 disabled pax from? they should be able to carry 10% of the seating capacity of the aircraft.
How many people travel on holiday on charter airlines and are disabled?????? I would hardly call blind a disability. If they can cross a busy road and find their own house again then they are a marvel in my eyes ( excuse the pun) . I think Ryanair were out of order here. Would be interesting to hear the opinions and regulations from other airline staff