No tool solves every problem. Put down the damned hammer and pick up a screw-driver once in a while.I agree with the above sentiment. I love a lot of different languages for various reasons. I often say that everyday I get closer to becoming a functional programmer because that style keeps rearing its head in my code. But, like anything it needs to be tempered.
It's all about balance and simplicity. I think the functional guidelines of trying to make most objects stateless and composition to the smallest and simplest are wonderful. The code you write reads well and if you try to restrict the places where you change, then it's easier to find bugs when problems arise.
The point is don't go overboard with your ideology. The end goal should always be readable code. Readable code changes information in few places. Readable code is easier to maintain. Readable code performs well. Readable code cares about the programmer that has to pick up the pieces once you're on to something else. Readable code is small. And finally, readable code is simple.
But, readable code takes thought. Design takes thought. Most of the zealotry that I witness is from people who want to remove thought. They think great code comes from restriction. It does not. It comes from freedom to have choice. Sure, you can make a bad choice, but sometimes the bad choice might be the good choice in certain situations. But, the choice requires thought. Any hard and fast rules should be looked upon with suspension. In the wise words of George Clinton:
Think! It Ain't Illegal Yet!
Oh, and if someone still wants to make religion and dogma out of anything technical (like the functional and XP evangelists), tell them to:
I'm going to think about making better code and designs.