Beware the Leaven of the Pharisees...

There's a train of thought that has been traveling through my head for quite some time now. It first popped up about 7 years ago, when I went to Tokyo for a couple of years to do some work for a group whos name need not mention here. While I was there, I noticed that my fellow missionaries broke down into 2 broad but distinct categories: the liberals and the conservatives.
First, for a definition or two. When I say liberals and conservatives, I don't mean it in a political sense. Instead, I mean it in a loose/strict sense. The liberals ranged from those who were on a mission because of all the wrong reasons and so they spent all their time goofing off to those who were wanpaku (Japanese, lit. like a little boy) to those who were doing things for the right reason and good people, but they wanted to enjoy themselves so they acted like most men would when put together with a bunch of other men - there was lots of horseplay, practical jokes, and so forth. The conservatives ranged from those who were majime (Japanese again, lit. a stick in the mud) to those who were anal about lots of things to those who wanted to enjoy themselves, but were just very straight about it.
I fell on the liberal side ever so slightly, and as such I was one of the many who deplored The Pharisee. When I say Pharisee, I don't mean the guys with phylacteries who strictly observed the law of Moses (a precursor to today's ultra-orthodox Jews), but rather one who strictly observes any set of rules or commandments. It was slightly perjorative, but what way is there to really describe these types? I suppose that overly anal retentive may work, but it just takes too long. Anyway, there was a constant battle between these two groups - not a real battle, but more a battle of minds.
The regular guys would be just having fun, goofing around, talking about life, and being regular in every way that you could expect from young men. The Pharisees on the other hand, tried to erase the past, like some sort of neo-Khmer Rouge/Jacobin/Commie-Nazis. When they started their mission, that was Year Zero and nothing happened before then. They never talked about anything other than the here and now. In addition, they couldn't just obey the rules we had, but they had to make up their own rules too. The thing that got me thinking of this was a letter from my brother who is in Minnesota on a mission currently. His prez doesn't want them to take any pictures that are unbecoming of a missionary. First, what does that mean, and second, why? That's just a little harsh. Second, why not let them loosen up? They'll have more fun and be happier as a result and that will get better results. So what's the deal with that? Thoughts?