Other mistake: During the early part of the movie, when Patton is in Morocco, you can see two kids visibly mugging for the camera as they do cutaways on two distinct occasions.
Other mistake: In the scene showing Patton's arrival in London, stepping out of a Packard limousine in the night, the car shown is a postwar model year, e.g. 1948. Patton did favor Packard cars, but this one could not have existed at the time.
Answer: "The front" means the front line, i.e., where the enemy is being engaged. He's saying that since the soldier isn't physically injured, he should be fighting, not (as Patton sees it) being a coward and shirking his duty.