That would be like putting a Japanese flag on my Grandfathers memorial, not very appropriate. General Robert E Lee fought for the Confederate States of America, not the United States of America. There are very very few things that would be inappropriate to put an American flag on, the General Lee car is one of them.
That makes about as much sense as dedicating and naming a car after General Ulysses Grant and painting a Confederate flag on it.
People are morons.
Actually, he fought for both. Robert E. Lee was a West Point graduate who fought in the Mexican-American War.