Forget flag burning. Here's a cutting-edge, freedom-of-expression, First Amendment issue, sure to be litigated soon in a courtroom near you. The Washington Post this week quoted A. Knighton Stanley, pastor of the Peoples Congregational Church, as follows: Urinating in public "speaks to a state of mind, an assessment of the condition of society. . . . In some ways, I see it as a perverse kind of public speech . . ."