It's so arbitrary with the NFL that it is starting to drive me crazy.
3irty1 hit the nail on the head. Rice isn't band because of doestic violence. He's banned because of a video. If there had been video, lots of Packers would have been banned over the years.

So domestic abuse in the privacy of your home might get you as short suspension. Domestic abuse in public gets you banned, but only if there is video.