Social experiment movie about power

Looking for this movie in which a group of young men are given roles of guards and prisoners. The whole premise of the movie is to show how power can corrupt men. Needless to say, they don't exactly end up ass  the nicest guards out there. I remember one scene in which they force one of the inmates who doesn't curse to say a swear word. He's probably religious.

I didn't really like the movie that much. It was boring, redundant and uneventful. It's certainly amusing how the guards suddenly become a bunch of Percy Wetmores.

It's an old movie. 90s or 2000s, if I had to guess.