The actual pain or inconvenience caused by a physical impairment is often much less than the sense of alienation felt by the person with disabilities. What is the kind of behaviour that the person expects from others?
A person with any physical impairment can live life with respect and honour, if he is not ridiculed and punished with heartless pity. He expects empathy rather than sympathy. If everyone looks down at him with a pessimistic approach, he may never be able to come out of his sorrow, and consequently, recline to his own secluded world. He is already in tremendous mental and emotional pressure. So, he expects others to be understanding rather than remind him of his disability.
In the play, Derry and Mr. Lamb, both are caught in a similar situation. Mr. Lamb, as an adult, is able to cope with such problems, but Derry, being a child, is not able to untangle this web alone. He develops a strong liking for this old man because he spoke the words a person, with such problem, would want to hear.