The Southern Christian Leadership Conference is a hallowed name in the annals of American civil-rights history, having been co-founded by a group of dedicated leaders that included its first president, the Rev. Martin Luther King Jr.The very nature of the nonviolent movement the group started, growing out of the Montgomery, Ala., bus boycott of 1955-56, dictated that those demanding civil rights had to exhibit an uncanny display of civility even in the midst of humiliating and retaliatory circumstances. They were taught how to resist without taking on the traits of their abusers.That lesson appears not to have been learned -- at least not well enough -- by the leader of the organization's local chapter, the Rev. Kyev Tatum. Or so he demonstrated in a squabble with the Arlington school district.Tatum, a graduate of Fort Worth's Trimble Technical High School and the University of North Texas, shows a passion for education and seems to be concerned about the education and fair treatment of all children. Most recently, he has been advocating "school choice" as an alternative to public schools that he thinks are failing youngsters, particularly those of color.But while institutions need to hear from critics as well as advocates -- even those who agitate and irritate -- Tatum often goes too far.He did so recently with a racially tinged insult to an Arlington school board member and a toothless call for a boycott of the city's merchants.The spat stems from a January incident in which an Arlington junior high special education teacher admitted pouring pencil shavings into the mouth of a sleeping black student. The teacher is white.Arlington school officials reprimanded and suspended the teacher for two weeks initially, and she was later placed on leave when the student's parent made additional claims.Because it's a personnel matter, district officials haven't made many details public. But Tatum has been quick to claim that the district is infected with "institutional racism," though he offers little to substantiate the assertion.According to a Star-Telegram news report, Tatum sent an email to a Hispanic trustee, calling the board member "an arrogant Mexican racist," and at Tuesday night's board meeting Tatum advocated a boycott of Arlington.Surely the minister realizes that he damaged his credibility by resorting to a racist comment that crossed the important line of civility.The Arlington school district might have systemic issues, but Tatum has not provided evidence of specific problems that can be addressed. Nor has he offered a credible reason why the city should be boycotted -- or, more important, how such a drastic economic action would help children.For the sake of the district as a whole, and especially for its more than 64,000 students, the adults in this situation should exhibit exemplary leadership. Open, honest and constructive dialogue are needed, not destructive confrontation or grandstanding.By coincidence, Thursday's school board meeting occurred on the 45th anniversary of King's assassination.Under King's guidance, the SCLC was better than this.