When you make a transform of the camera, or helper object, that is using a motion path, you are actually adjusting the motion path... NOT the object. So when you rotate the object, the motion path rotates at that time on the timeline. It IS a bit wonky... but has logic too... as long as you follow IT'S logic, instead of your own! ;) I agree with Mark. Setup your keyframes, then convert and use a 'Point at' modifier for best results. Good luck!