I have been reading Rusty Moore's blog (Fitness BlackBook) for over 1½ years now and was recently redirected to MDA.
I have been reading up on PB exercise (PB still makes me think peanutbutter every now and then) and to run fast for a bit (sprints), walk for a longer period of time and lifing something heavy is all very Grok. However, I LOVE body combat. I know its not technically PB but I don't care. It makes me smile it makes me happy and I'm not as grumpy after staring at myself in a mirror trying to punch as hard as I can.
What I mainly wanted to say here is that I think that exercise that you enjoy and have fun with should be encouraged (as long as its not being done obsessively).
So go and do something you love doing every once in a while, even if it may not be stricly PB : )