Bill is a member of Sleep Hallow Country Club in Westchester. I have several friends there who are also members. They all claim he's delightful. The true measure of a person is not how he behaves at work. We are not employed to make friends.
I think that in part Bill was gruff to his fellow lead actor because, much as the Delta House actors in Animal House didn't associate with the other frat's actors (like Kevin Bacon), it was about somewhat living the role.