
Revealing mistake: When Puffy the dog bites Ted and pulls him along, Ted digs his fingernails into the floor, they scrape along, making marks. If you look very closely you can see faint pre-made marks made in the floor, where he drags his nails along. (01:28:45)
Answer: Because he is ignorant and doesn't know anything about disabled people, he actually doesn't realise what he is saying is offensive.