I just posted something similar in another thread but I have absolutely no respect for the guys walking away from their prior obligations to be in movies. If you aren't holding a belt, or under contract, do whatever you want, it's your own career. If you signed a contract saying that you were going to be a fighter for X amount of time, you need to do your job, simple as that.
I agree completely with Dana, I would be absolutely furious. I would really try to do whatever I could to legally prevent it from happening to let people know that it is completely unacceptable to do things like this. I'm sure their contracts are going to containing a new clause pretty soon about abandoning your obligations to act in movies.