I vote a beat down. I feel your pain with this situation. I had a similar one, only with drinking. one of my room mates, at the time, got pissed cause we were up late partying the night before he had to work. came out pregnant doggin about it. I told him that he had done the exact same thing to me on numerous occasions. he got bent about that, and I told him it was either fight it out or leave. He chose to fight it out and lost. Shortly after that, he moved out. they are stoners and probably wont put up much of a fight.
If you do open a can of whoop ass, make sure they know why they are getting their asses kicked. Kinda like a puppy, you cant just tell them "no pissing in the house" gotta show them by rubbing their nose in it. Anyway, what ever you choose good luck.
Oh and dont let their crap attitudes ruin your good deal you got going on at that house.