Can You Prosecute Somebody for Spitting in Your Face if You Punch Him in Response

As people before have mentioned, you run the risk of being criminally charged yourself if you report. From a personal experience standpoint, you really don't want an assault conviction on your record, and especially one that you have to explain occurred in the workplace because any future employer is likely to see you as a liability, and its going to make it hard for you to find good work in the future. Just something to think about.