One more time, here we go.
RAW (Rules as written)
Glory Hog must do one of the following:
1) Shoot at a vehicle if in range.
A) If the vehicle is destroyed, the Glory Hogs are done for the turn
B) If the vehicle survives, the Glory Hogs don't charge it though
C) If the vehicle survives, the Glory Hogs charge it in the assault phase
2) Don't shoot a vehicle in range and must charge in the assault phase
As written, only the above can happen. Glory Hog doesn't have a special ability to charge a different unit then the one they shot at. Again, the inclusion of the word or in the rule. If it meant every turn they had to charge a vehicle, the rule would say something like "they must shoot a vehicle in the shooting phase and charge a vehicle in the assault phase. These can be different targets." It doesn't say anything like that.
RAI (Rules as intended)
1) The Glory Hogs must shoot at a vehicle in range.
A) If it survives the shooting, then they must charge that same vehicle.
B) If it is destroyed, the Glory Hogs are done.
Again, NOTHING in the Glory Hog rule conflicts with anything in the rulebook. You can not charge a unit if you shot at a different unit in the shooting phase. All the Glory Hog rule says is you must shoot OR assault each turn, at the minimum. By including the word AND, you can still charge the same vehicle you shot at if it wasn't destroyed.