But, this is not a reliable way to get knowledge about the world. Just because everyone around you says that A is B doesn't mean that it is, it simply means that that's what the people around you say. Go somewhere else, like that souk in Morocco, and they'll be equally convinced that it isn't.
For a culture to be stable I suspect it's important that most people try to make the effort to fit in without challenging the underlying assumptions of the group. But when that culture faces a challenge, and needs to stop doing some of the things it has been and start doing some others instead, this habit of conformity becomes a liability rather than an asset.
The obverse oft his tendency for individuals to fit in is that we tend to judge the person presenting the argument - to see if they fit in - rather than the argument itself. We question the character of the person rather than the details of the argument. Even I find it hard to give David Cameron the benefit of the doubt and take what he says seriously rather than simply saying to myself "well that's the sort of thing he would say"
Now, a common tactic that's used against someone presenting an argument we'd rather not agree with is to accuse them of hypocrisy. Though sometimes this clearly doesn't work - How can you say murder's wrong when you've already gone and murdered someone? - a lot of the time it does. How can you lecture me about emissions from aircraft when you went on holiday to Majorca? How can you say we ought to consume less when you've got an i-pad?
Those of us attempting to come to terms with the environmental and ecological impacts of the way we live come up against accusations of hypocrisy almost every day. We might try hard to explain that what we're wanting are structural changes in our towns and cities, changes that would bring where we work closer to where we live, changes that would make it safer and more convenient to walk or cycle than to take the car, but the charges of hypocrisy stick.
But, if you were a member of the Selfish Greedy Party and believed that we're all simply in it for ourselves, and that everyone who didn't was simply trying to excuse their own failure, then it would be very hard to ever be accused of hypocrisy. Even then you could excuse the odd random act of kindness as really being made out of self interest, as indeed, you'd no doubt argue, are all of those made by everyone else.
So, whilst being a hypocrite may not be quite the best thing to be its probably better than not being able to be one at all.