IT'S THE SORT of ugly news that local leaders hesitate to talk about for fear that any official reactions may generate still more trouble -- but Montgomery County Executive Charles W. Gilchrist has decided he can no longer remain silent on the subject of racial, religious and ethnic incidents in the county. His concern is justified:

Item: On June 25, five white teen-agers were charged with using a stolen fire extinguisher to spray a caustic solution of ammonia and anti-freeze on a group of black people in Wheaton.

Item: On June 7, the car of a Rockville man was tarred and inscribed with an anti-Semitic remark; less than two weeks before, an anti-Semitic inscription was written on the door of a school in Rockville; and the day before this, a swastika was painted on the sidewalk outside a synagogue in Wheaton.

Item: On April 4, the home of an Asian man in Silver Spring was spray-painted with racial slurs and obscenities.

Item: Leaflets urging students to join the "Klan Youth Corp" have been distributed in some county schools, complete with application forms and a picture of a white youth with manacled hands over his head, breaking a chain and advocating "white power."

These are just a few of the 39 incidents -- including cross-burnings, harassment, vandalism and assaults -- that were reported to police and the county's human relations commission during the first six months of the year.For all of last year, the total reported was under 25, and the year before it was about half of that. As Mr. Gilchrist has noted, "This kind of attack has the inevitable effect of unnerving thousands of people, not just the 'prime targets'. . . . These are not pranks. . . . These are savage assaults on the sensibility of our fellow citizens. . . ."

We don't know whether the situation in Montgomery County is any better or worse than elsewhere, but the record of reported incidents is longer and more specific, and Mr. Gilchrist has been meeting with community, religious and political leaders to figure out ways to deal with it.

Police do note some patterns. In Wheaton, they report, whites and blacks are pitted against each other; in Silver Spring, blacks against Latinos; in Rockville and Potomac, Jews are likely to be victims. And many of the incidents seem to be the work of teen-agers.

From all this have come some proposals that deserve consideration. Mr. Gilchrist says he's confident that the prosecutor's office will transmit the "unmistakable message that this kind of conduct will not be tolerated in Montgomery County." Gov. Harry Hughes has spoken out too, calling on prosecutors around the state to do battle against the "misguided hate-mongers who seem to emerge during times of economic stress and emotional strain."

In addition to calls for vigorous prosecution, there is work to be done in the schools, through discussions aimed at countering bigotry and careful monitoring of activities by outsiders on or within sight of the school grounds. mOf all people, the young should be learning tolerance and speaking out against racial, religious or ethnic bigotry.