In many instances, inaction is just as powerful as action. By refusing to use force to stop the threat of facism, so-called pacifists enable the spread of the violence they claim to oppose. Though pacifism looks good on paper, it cannot be feasibly implemented into the real world without serious moral issues.
Moreover, this argument implies that all violence is equally wrong and unjustifiable, when in reality, some violent acts are far worse than others. Namely, punching a Nazi is far more acceptable than facilitating the genocide of an entire race of people. It is fallacious (and profoundly Kantian) to argue that violence is never acceptable, especially when considering that some lesser violent acts can be used to prevent greater ones.