Muggeridge and the bishop sounded incredibly pompous and anachronistic, even in 1979. The Catholic church particularly organised a fabulous publicity campaign for the Pythons. Every few days yet another fossilised Arch something-or-other relic turned up in the news to complain of a film they hadn't even watched.
I thought Meaning of Life carefully directed at ridiculous Papal edicts and Catholic dogma, vs equally ridiculous CofE flavoured Protestantism, rather than anything against Christianity itself. It was wildly heretical - against the church, but not blasphemous. And had the Galaxy Song, so should have been far more successful than it was. :)