Pacifism does require sacrificing, but it doesn't necessarily render you helpless. Also, I think Gandhi said that violence is still better than cowardice. If I'll ever use pacifism as an excuse to be lazy or cowardlike, you can call me and tell me I should be ashamed of myself. But if someone beats me up, who's the crook, the one who beats me or myself?
I believe that in a situation like this I would employ violence in order to try and escape, but by far I've never needed violence to accomplish anything useful.
But you know there ARE self-defence methods such as judo that allow you to simultaneously avoid getting thrashed by rendering the aggressor unable to be violent with you not having to really hurt him, though this may be regarded as violence as well. I don't see it as violence but rather limiting someone's physical freedom in order to convince them not to be violent? Man, I've got to start taking judo lessons, now that I think about it.
If you have to choose which one doesn't work, pacifism or violence, it's the violence.