Catching jabs out of the air? Stepping back? From what I recall, the last time I stepped back to avoid a jab, there was a straight right waiting for me. A jab is a setup punch. Primarily, it judges distance, blinds and creates openings by illiciting a response. Over reacting to one can be a very bad idea. Boxers (who deal with it most often and most effectiviely) sometimes deal with a jab by bobbing and weaving and slipping inside the stiff end of the punch.
All I can say is that's what I learned from a highly qualified, excellent sensei. Well, I can say one more thing; I wouldn't cuss out Mike Tyson then try it on him.