Perfect Ending, there is a Seligman in every guy
Although we don't have any details about Mr. Seligman, we know enough about him to understand what type of person he is. As a guy, I actually believe that all man have some form of Seligmanism in them. Most of us are sincere but sometimes our sexual desires overpower us.
However, this is a very extreem scenario, in which Mr. Seligman actually convinced himself that he is a-sexual in order not to be confronted with the fact that he is a loner disparately yearning for human contact (just look at his living conditions and the fact that he is still a virgin at age 65). Instead he hides from humanity behind his books and intellectuality.
Joe is his complete opposite. She has lived life so hard that her lady parts don't even work anymore. This explains Mr. Seligman's odd and out of place metaphors, that he uses to relate to her story as he really can't.
For the first time in his live, he finely has the urge and the courage to act on his sexual desires because of the close connection they forced. However, without any experience in human contact he seriously lacks the social skills on how to approach a girl in such a situation.
Joe is of course furious. Not only did he try raping her when she was most vulnerable, but she also feels extremely betrayed by the first person she actually trusted as a friend, proving to her that society doesn't understand her.
In reality Mr. Seligman's sexual and social skills are still stuck on "teenager" level, something he was able to hide with his intellectuality. Again the opposite, Joe's ration thinking is limited expecting a total stranger to truly care for her. At the end of the day, they simply didn't understand each other like most of us in life and in this case the result was pretty deadly.