I don't think TC sees "following rules" and "winning" as mutually exclusive events. To Tom Coughlin, winning is a function of many things, including following rules. In his view, if you start bending the rules to favor certain players (like starting running backs), others see this...it creates some chaos...which leads to further chaos (what happens when the next person breaks curfew?)...which leads to a breakdown of the system, the inmates running the asylum, and the team becomes like the Dallas Cowboys under Wade Phillips...
Also, we don't know if this was a first violation. If memory serves me correctly, I believe Plaxico Burress was benched (back in the season he shot himself), and it was due to multiple violations...I think. So, it's possible this was not Bradshaw's first violation. Also, with someone like Bradshaw, who has a history (albeit small history) of trouble, Coughlin might have wanted to get on top of this before it became a larger problem.
When watching the game, and it was first reported, I thought Coughlin did the right thing...and I admired the fact that he would stick to his principles even though it might cost him his career. Of course, I thought he might hold Bradshaw out only for the first series or (at worst) the first quarter. I wonder if, had Jacobs not been running with such authority, if the punishment would have been less severe. Somehow, with Coughlin, I doubt it.