Flags and anthems and patriotic display can inspire love and heroism but they can also bring out the worst in people. Add war, social unease, sports, and race and the fists are likely to fly. This was the context of one of the Court’s most humiliating mistakes—one that led directly to violence in the streets, required the Court to eat its own words, and may teach us a lesson in tolerance today.

Let’s be clear what is at stake. Kaepernick has not expressed allegiance to or support for the nation’s enemies. He has not made any criticism or attack on America’s military. He has not refused to do his job as quarterback. He has not asked anyone to take down a flag, or sought to veto the playing of “The Star-Spangled Banner.” He has not asserted a right to discriminate against anyone who does want to stand and salute during the National Anthem.

Kaepernick has simply indicated that, for reasons he is willing to explain, he himself will not pay personal homage to our nation’s symbol. Others may think he shouldn’t feel that way, but he does, and he will not pretend to feel what he does not.

That issue—the compelled assertion of personal allegiance, a requirement by the state that individuals express feelings they did not hold—brought the flag before the Court in 1940, and, after the decision, led directly to blood in the streets of American towns like Litchfield.

Minersville School District v. Gobitis arose in 1935, when two Jehovah’s Witnesses, Billy and Lillian Gobitas, refused to engage in a required flag salute and pledge of allegiance at their Pennsylvania elementary school. For Witnesses, pledging allegiance to any human symbol is a violation of the Second Commandment: “You must not make for yourself a carved image or a form like anything that is in the heavens above or on the earth below or in the waters under the earth. You must not bow down to them nor be enticed to serve them … ” The local school board expelled them; local people boycotted the family store.

Lower federal courts supported their right to refuse the pledge. The case, however, reached the Supreme Court in 1940, as German armies were grinding toward Paris. The justices rejected the children’s religious-freedom claim to an exemption from the flag-salute requirement. (Poignantly enough, the Court could not even be bothered to spell the children’s last name correctly.) In the majority opinion, Justice Felix Frankfurter wrote that “We are dealing with an interest inferior to none in the hierarchy of legal values. National unity is the basis of national security.” The legislature must have the freedom to promote that unity by requiring children to pledge allegiance, he wrote, and religious objections were no defense.

As outlined in Shawn Francis Peters’s Judging Jehovah’s Witnesses: Religious Persecution and the Dawn of the Rights Revolution, the court’s decision set off a wave of mob violence and persecution. (The quote from the Litchefield vigilante comes from the book.) Witness meeting houses were looted and burned. Citizens held public bonfires of Witness literature. Witnesses, tied together with ropes, were frog-marched out of towns in many states. Witnesses publicly soiled themselves after being force-fed castor oil. A Nebraska mob castrated a Witness. Law enforcement did little.“They’re traitors—the Supreme Court says so,” one Texas sheriff told a northern journalist.