So yes... I don't understand the violence.
Even though I agree that a man is morally obligated to support his children and that it is his nature to do so, I have deep concerns about legal enforcement of such an obligation. Especially when men are being ordered to get a job or go to jail. It sounds a lot like slavery. If anything, when push comes to shove, the only one who should be the servant of another is the child.
If a man fails to care for his own children, he is already going to lose plenty without losing his property and his freedom. Sure, a man should be held responsible for his own actions. On the other hand, there are plenty of women who feel that what happens inside their own body is nobody else's business. For those, I don't think the result of that which is no one else's business should be anyone else's responsibility.