Can't be told.
In my opinion...
If something even suggests racism and the creator refuses to change it or work with it, than yes, it's racism. 'Cause although it's not flat-out racism and there may be another alternative meaning, it also means that the creator doesn't mind having the flag labelled as racism because it can be true as well in his views.
But, if even then it can't be changed and it shows racism non-blatantly, but has a GREAT alternative meaning, than no, it shouldn't be considered racism. It would be playing the race-card on everything.
In this car, since it's representing the states that they stood for which also stands for slavery, unfortunately. They can't change the history of the states, but they can change themselves within individually and can stand for their homeland.