The thing I don't get about "Equilibrium" is Taye Diggs. Prozium is supposed to suppress ALL feelings; happiness, anger, sadness, etc. Preston was capable of feelings, but they only started truly surfacing when he stopped taking his doses (by the way, I think Christian Bale was perfect for this role seeing as how all he had to feel was first nothing, then anger/rage. Keanu Reeves would have been perfect...but only in the first half, that robot). So everyone, including Clerics, were supposedly suppressing ALL emotion by Prozium injections.
Then why does Taye Diggs always seem either happy or angry throughout the whole movie? He's smiling because he triumphed, or when he is challenged is clearly enjoying the challenge. He's also yelling and screaming, angry and showing it when things do not go his way.
If you ask me, someone ELSE wasn't taking his Prozium.