A good starting point in considering the OP’s proposition is to understand the law of the state in which the offense occurs. I am in PA so my actions are governed by the following section of PA law.
(a) The use of force upon or toward another person is justifiable when the actor believes that such force is immediately necessary for the purpose of protecting himself against the use of unlawful force by such other person on the present occasion.
(2) The use of deadly force is not justifiable under this section unless the actor believes that such force is necessary to protect himself against death, serious bodily injury, kidnapping or sexual intercourse compelled by force or threat;
The important text was bolted by me. In PA use of any force requires that you be threatened by the use of force. Demanding for your wallet is not in itself the use of force. Threatening you is not the use of force. Brandishing a deadly weapon in PA is considered use of force. So if the perp presents a deadly weapon you can use force and even deadly force.
What would I do? It depends upon too many possible factors in the scenario to provide a brief and concise answer. I would only know what I might do if I were in such a situation.
