the movie doesn't properly establish Devereaux as a villain

In his first scene in the movie he protests against putting the army in New York City to stop the terrorists. He says it would be a very bad idea. But then as soon as he gets to NYC with his troops he starts abusing his power. He doesn't even try to restrain himself. It's as if he and the guy who said this was a bad idea were 2 completely different people. It would have made more sense if he was promoting the idea of putting troops in NYC instead of protesting against it. And since he was the guy protesting against the army occupation he should have been shown trying to resist the abuses he committed. Someone outranking him and ordering him to do the bad things should have been the real villain.