While Mr. Muggeridge and the Bishop's harangues can be quite tedious to get through at times, the whole thing is interesting because of how well they obliviously make Cleese and Palin's point for them. As Cleese futilely tries to tell them, the point of the movie isn't to ridicule the figure of Christ, it's to ridicule "closed systems of thought." The film is meant to encourage people to think for themselves, to approach matters—including religion—with an open mind and critical thinking. Mr. Muggeridge and the Bishop do an excellent job of showing the pitfalls of such closed systems by clearly having had their opinions of the movie set in stone before they ever saw it and by stubbornly brushing off all of the Pythons' attempts to explain to them how they'd misinterpreted the film.
You can find the second part of the video and the rest of my thoughts below the fold. (By the way, ignore the titles of the embedded videos. :P They were clearly uploaded by another person who isn't keen on listening to what the Pythons were actually saying.)
I've made watching Life of Brian a yearly Easter tradition. It really is an excellent film, and as the Pythons try to point out, it only intends to mock those who would follow blindly and does not lampoon the person or the holiness of Jesus of Nazareth. Jesus appears only briefly, is played by a serious actor (rather than one of the Pythons), and his lines and actions are taken straight from the Bible. As I've seen it put by the Pythons elsewhere: the film is certainly heretical because it questions religious institutions, particularly the various Christian sects; but it is not blasphemous, since it doesn't mock the word of God.
The two older fellows will hear none of that, however. Despite having apparently been given a screening of the film before the debate, they stubbornly refuse to see that the character of Brian is not intended to be a caricature of Jesus. Brian is merely the point around which the humor and commentary of the film revolve—humor and commentary which aren't directed at the Messiah figure but at the followers of the Messiah figure. People mis-hear, mis-interpret, and over-interpret the words and actions of Brian, quickly building up a religion around him against his wishes. It's meant to show how imperfect the transmission of ideas can be, and the pitfalls of credulous thinking. It implores you to think critically about all aspects of religion and to come to your own, well-reasoned conclusions rather than simply going along with group consensus or tradition or wishful-thinking.
It seems obvious that Muggeridge and Stockwood are of the opinion that anything that approaches Christianity with any sense of humor is inherently corrupt. They keep trying to make the point that a young child exposed to this movie might come away with an inaccurate interpretation of the gospels—that the child might wind up seeing the story of the crucifixion as a bit of a farce. And? It's their job to convince people that the story of Jesus is sensible and worthy of belief. Were they under the impression that the Pythons were obligated to present a straightforward retelling of the gospels? The film isn't meant to give you a comprehensive understanding of the New Testament; it's meant to get you asking questions about the New Testament.
Similarly, the film also isn't meant to be a definitive refutation of the New Testament, but at one point the older gentlemen start arguing as though that were the case (after an odd moment where they seem to be under the impression that the Pythons think their movie should stand side-by-side with great works of religiously-inspired art like cathedrals). Again, all the film wants you to do is ask questions. If those questions eventually lead you to the conclusion that Christianity or religion in general is false, then so be it. They might also strengthen your belief. The main thing is that you're challenging your beliefs in the first place. The answers aren't as important as the questions. The Pythons are of the opinion (as am I) that your beliefs should have a rational and defensible basis.
At one point Cleese asks Muggeridge whether there's anything that could change his mind about Christianity. He asks because he thinks a worthwhile belief should be falsifiable. If there's no evidence that could disprove a claim then the claim is almost certainly detached from our realm of tangibility and thus from the ability to be relatively certain about it. (I discuss such claims in Part 3 of my "Why I'm an atheist" series.) Muggeridge tells Cleese that yes, there are things that could change his mind and that all Christians struggle with their beliefs, but I wish Cleese had pushed further on the issue (unfortunately both the Python boys were far too polite for that sort of thing throughout the debate). Because despite what Muggeridge said, I must admit that I don't believe him. I don't think there's anything that could change his mind about Christianity, and I don't think he or most other Christians actually approach their beliefs critically. They may doubt them from time to time, I'm sure, but I'm less convinced that they genuinely apply critical thought to them. Faith—the act of believing in something for its own sake and even in the face of contradicting evidence—is seen as a virtue in religion. Willful ignorance is not only accepted, but actively encouraged. The Pythons see a problem with that, and with Life of Brian they're trying to convince you that whether you believe in the story of Jesus or not, that belief should be based on a critical examination of all the available evidence, and not on a blind act of faith.
When I look at Muggeridge and Stockwood I see two men who have made up their minds for good and who will block their ears to any evidence to the contrary. I see two men who refuse to ask questions about what they believe. Just as they'd drawn all their conclusions about the film before they even saw it and then refused to acknowledge that they'd misinterpreted it, so too have they decided to never turn a critical eye to their Christian faith. To me, it's a dishonest way to live.
Again, I do think that watching the whole segment is worth it, but that could just be my love of anything Python coming through. At the very least, you can hear the interesting point that Muggeridge makes about Mother Teresa, in which he seems to imply that she would see no point in helping the poor if Jesus as a person never existed, which (as I mentioned in Part 2 of my "Why I'm an atheist" series) I find quite deplorable and just a bit frightening.