It has been a rough few days for race and sports in Boston. But in the outrage over the detestable behavior of Bruins fans, it’s easy to forget how far we’ve come. Here, then, is a reminder. It’s the story of “Hulu’’ Lou Montgomery, a halfback on the Boston College team in 1939 and 1940. And of a BC alum named Mark Dullea, who wants the mistakes his alma mater made over 70 years ago to be properly acknowledged, the school’s transgressions against its first black football player - and its own values - made right.