While I agree that they can make their own movies, the historical record proves them out for having a beef if the French were given insufficient credit (I have NOT seen the movie yet). The evacuation was defended by about 38k French troops from their 2nd light mechanized and 68th infantry Divisions who held until they had to surrender.
A piece of ironic history is that most of the evacuated French military were quickly repatriated back to France only to be caught in the French Surrender on June 17th of 1940. One can imagine their feelings after having made that tremendous effort to survive the retreat and evacuation then to have that escape turned into ashes so soon after!
History and accuracy and the record are at the mercy of Hollywood producers on both, or all, sides of the political spectrum.
Throwing a bone to the sacrifice made by the French is not too much to ask.
After all French boys were at the mercy of their efete leadership, but they were there, nevertheless.