I am not sure what you are looking for here when you ask "[h]ow will a public defender defend the defendant?" First, I would assume that a public defender as with any attorney, will be a zealous representative and advocate for his client. The translation is that he or she will do everything within ethical and legal bounds to defend his client. Second, whether the reason the defendant hit you is ridiculous or not does not always parallel whether a legal defense will have strength. However, you can expect the defendant's attorney to come up with his best defense/strategy.
The information provided herein does not create an attorney-client relationship. The information provided is to suggerst some general principles and should not be relied upon for client decisions. Only upon the hiring of counsel can such advice be custom-tailored to the client's specific situation and needs.
How can we know his public defender's strategy which is confidential to the defendant and not available to the public? If you are asking how the prosecutor can nail this guy, despite his PD, ask the prosecutor, not us.
He will defend him just like a private criminal defense attorney would. Contrary to popular misconception, public defenders are not a lower class of attorneys, nor are they not attorneys as some people believe.