How does Rowdy's father's reaction help to explain why rowdy is the way he is?

Junior gives Rowdy's father a picture to give Rowdy. Rowdy's father says that the picture is "kind of gay." It turns out Rowdy is actually home. He flips Arnold the finger from his window We can understand why Rowdy has such a passive/aggressive personality. Rowdy's father  has a very narrow attitude. He would treat his sun with the same acceptance and rejection he displays with Junior.