Do you think that's what the author was thinking about? I don't think so. So if he wasn't concerned with being seen teaching his sons to distrust, fear, and dislike Southern whites, which he obviously did right there in the middle of the restaurant, what exactly is our reciprocal obligation to him? He didn't trim or back and fill or make nice -- do you criticize him for that? No.
Many black people of middle-age and older have distinct memories of a less-enlightened time in our nation's history.
By that do I take it that you mean that when Side A is winning, that's ontologically good, but when Side B is winning, that's metaphysically bad? Sounds like you've swallowed some Northern liberal "march of history" progressivism.
Blacks lost as much as anyone when liberal and statist principles advanced on the back of the civil rights movement.
Rather than argue for their POV, liberals have always gone for the power play. They tried using inside politics in leadership forums to install their program on desegregation in the South in the 1950's, and when they encountered significant resistance from people who hadn't been consulted and were never conciliated, they immediately turned to the federal government and the courts. Liberals don't debate issues with scum like us: they just articulate a position and then try to enforce it "by any means necessary", while justifying it by rhetoric and by pointing at whatever the other guy is doing wrong. Liberalism owed its largest debt to the Ku Klux Klan bombers and the liberal journalists who knew how to use them, and there was no justice in any of it, only a power struggle won by the undeserving -- liberal statists. Everybody else lost. Blacks thought they "won", but the rights they won were less than the whites had had before the civil rights movement.
Those memories are highly unpleasant, and they see the flag as symbolic of those memories.
The Klan didn't really use the flag. The segregationists did, and they rallied against (in particular) Eisenhower's stand on enforcing the liberal court decisions on integration, and his sending the 82nd Airborne Division to Little Rock to chase white mobs off the street and away from the schools.
Once the liberals won in court, they put the Executive in a box, about whether to enforce the court decrees. After Eisenhower made his decision, the segregationists were fresh out of luck, out of time, and out of friends. That's when they ran up the battle flag, hoping to inspire a united front against the federal government. They failed, because history put Lyndon Johnson in the White House, who attacked them with all the tools of the "imperial presidency" and broke them by threatening them with mass jailings of school boards and other public officials. That was Leon Panetta's first real public-service job, threatening the slowfooted in Louisiana for Lyndon Johnson. The deal was, if Panetta called someone in, he explained to them that they couldn't even resign their offices or do anything but exactly what he told them to do, when he told them to do it, or they would spend time in a federal penitentiary, and the rest of their lives as felons and ex-convicts. That's what liberalism means, where the rubber meets the road. Northerners loved it, of course.