Terry's response is more understandable, and more normal. That is, if your child becomes a vocal, in-everyone's-face, promote-immorality activist.
No, Terry's response is not understandable, given the high regards his son had for him. I saw nothing "in your face" in interviews with the son, but certainly did with the father. He rejected his son outright and told the world he is no longer welcome in his home. Randall Terry's hatred for his son and his lifestyle was the only "in your face" attitude.
My children all turned out straight, but if one of them hadn't, I would hope I would have emulated the Vice President's response, rather than that of a well known hate monger.