STANDING AND saluting the flag during the national anthem shows respect and patriotism. All Americans should do so, absent some compelling reason to the contrary. Since 2016, varying numbers of National Football League players have knelt on the field or otherwise deviated from the ritual because, in their eyes, there is a compelling reason: to protest police excesses, which disproportionately affect people who, like the majority of NFL players, are African American. Even if you disagree about the substance or manner of their protest, these men are following their consciences and exercising their constitutional rights. That, too, is patriotism.

The potency of their statement can be measured in part by the backlash it has caused; it is the nature of protest to cause discomfort. Rather than pause to consider the merits of the players’ cause, President Trump has fomented and exploited that backlash, urging the NFL and its team owners to punish the players. And it would appear that the controversy Mr. Trump helped to aggravate, and which has cost the league ticket sales and TV ratings, has now brought the league to its knees. The NFL has announced a policy that essentially gives players three options: stand and “show respect” during the anthem; stay off the field until it’s over; or face “appropriate” discipline. The fact that compulsory patriotism is the hallmark of dictatorial systems seems not to trouble the NFL’s confused and frightened moguls.

Meanwhile, in Milwaukee, there is fresh proof that the NFL players are not just overprivileged complainers, as some of their critics maintain; the abuses that concern them are real, and even pro athletes are not immune. The police chief of that Midwestern city just apologized for a January incident in which members of his department tackled National Basketball Association player Sterling Brown, who is black, and forced him to the ground with the help of a painful stun-gun shock, because — well, for no good reason, at least none that’s visible on police body-camera video.

Mr. Brown had parked across two designated disabled spaces outside a drugstore. Rather than issue him a ticket or ask him to move the car, a Milwaukee officer escalated the matter by rudely and sarcastically challenging Mr. Brown, calling for backup from more police and, eventually, throwing him to ground with the help of several other officers and the stun gun, before briefly jailing the basketball player. When the officer told him, “I own this right here,” Mr. Brown responded, “You don’t own me,” but never raised his voice, brandished a weapon or engaged in any other violence. No charges were filed, and Mr. Brown was released after a short time, bruised but, fortunately, not more seriously injured.

Mr. Trump may denounce the NFL players as much as he wants. The league and its team owners can try to muzzle them. Unless and until police misconduct such as that visited on Mr. Brown is addressed — unless and until it arouses as much popular indignation as do protests against it — the players will, in our view, have amply compelling reason to express themselves.