PLEASE, NO excuses for the rampage of Saturday. Even to grace those mindless rock- and bottle-throwers and looters with the label of "anti-Klan protesters" gives them a status they don't deserve to enjoy. It is equally bubble-headed to explain the violence and destruction as an outburst in reaction to unemployment, the Reagan administration, Israel, South Africa or any of the other named objects of complaint. All it took was a handful of practiced delinquents and trouble-hungry instigators to stir things up.

There are some episodes that have no handy, built- in insights or great moral lessons to impart--but only self-evident truths to be underscored. Foremost among such truths this weekend is that the Ku Klux Klan is no less despicable because a crowd of vandals behaved so recklessly. If the Klan members' bid for attention and trouble was an objective, consider it accomplished. But they were still bit players in the action, their message no less ugly than it ever has been.

Who got hurt? Not the Klan; all it may have gotten is the last laugh, and that's a shame, too. Bystanders were physically hurt, police officers were injured, people with messages of tolerance and words of peace were knocked around. Worst of all, the people of Washington--those whom the Klan would like to hurt the most--ended up with wounds that will be long in healing.

Police Chief Maurice Turner, as much as anyone, had his hands full and responded professionally to the pressures. So did the rank and file, who were stretched beyond instant-reponse capabilities in many instances but who did what they could to arrest as many suspects as possible. Prosecution, we expect, will be vigorous. This may not calm the understandably furious merchants whose downtown stores and offices were destroyed, but everyone deserves assurances that the laws of the city are being enforced as effectively as possible.

Washington has been, and will continue to be, host city to demonstrators with messages that run the full range, from the bigotry of the Klan to what many would consider to be significant and important petitions to their government. In the past, this city has reacted as well as any in ensuring the rights of peaceful protest while protecting all people from violence. That was the assignment of the authorities on Saturday, and it will remain so.