They are discussing a film that was seen in the past. This is definitely an action that happened in the past,not polite present.

1) This conversation COULD be about the IMMEDIATE past. It could even take place between my wife and myself at the end of a film when the credits are rolling. 2) It could not be about the present. I could not whisper it to my wife DURING the film. I could whisper "Are you enjoying this?" I would use the present tense. 2) "I was wondering if" isn't polite because of being in the PAST. It is polite because of being expressed as a GUESS. They key words are "if" and "wondering." Let's say the whole sentence is "I was wondering if you would like to pay me the money you borrowed." The key words are "if"--you are pretending you don't really care, and that it's OK if they pay or they don't. "Wondering" suggests the thought just sort of occurred to you. For some reason "was wondering" sounds better. But one could also say "I am wondering if this happens to be a good time for you to pay me back the money..."

This is the past. B saw the film in the past, maybe yesterday or last week, and A is asking B what he or she thought about it at the time.