I didn't say Christians or theists are "necessarily" hypocrites. I said most of them are. The world would be a very different place if most so-called religious people actually believe what they say they believe, if they lived as though their religious beliefs were true. Some priests, monks, and religious extremists do so, but most theists care more about fitting into a social club than in theology. Their "faith" doesn't amount to real conviction.
What they really believe is what dictates their actual behaviour. We know their operative beliefs are secular rather than theistic, because living your life as though theism and certain religious scriptures were true would compel you to act in a way that would seem insane in civilized society. You'd have to live as though God were watching you all the time. You'd be an off-putting and potentially very dangerous fundamentalist. That would cost you your earthly happiness. In short, you'd be Christ-like, which few Christians are on an hourly or daily basis.
And I didn't say Lewis was naive. I said that popularizers like him and Craig defend commonsense and intuition to dissuade Christians from getting too far into philosophy. Once you trust commonsense and intuition as sources of fundamental truth, you can protect your religious faith from doubts, since we're hardwired to socialize and to personify everything to understand it. (Science gets around that to provide us with the objective, often counterintuitive truth.)
This was the logic of Mere Christianity, to show how Christianity follows from commonsense acceptance of moral laws. Mind you, Lewis must have been pretty naive to think his trilemma argument would fly. Specifically, he was naive in assuming the fourth option wouldn't become widely known, namely that if Jesus was historical, he likely didn't say most of what the New Testament attributes to him. That is, Lewis was naive in ignoring the scholarly view of the historical Jesus that's based on the critical-historical approach to the Bible and to Christianity's origin.