The Supreme Court offers the last public venue in Washington where there can be serious, uninterrupted give-and-take on controversial issues because no television or still cameras are allowed.It has to stay that way.That was my first reaction Wednesday after the court's two hours of oral argument over the constitutionality of the Defense of Marriage Act. I have regularly gone to listen to arguments in the court over the past 30 years, often to hear my son, who has argued 23 times before the court, and often since I got a law degree a dozen years ago.Wednesday, I was among the lucky 400 or so with a ticket.There has been an argument for years that the public has been blocked from witnessing the court in action and that allowing television cameras in "would be a terrific thing," as one TV commentator said Thursday.The loudest voices for bringing in the cameras mostly come from the news media, particularly those with TV networks or stations.But television would change the court for the worse, as it already has for Congress, presidential campaigns and much of the country's political life.In the 1960s, I spent two 18-month sabbaticals from journalism running investigations for the Senate Foreign Relations Committee. Working directly for its chairman, Sen. J.W. Fulbright, D-Ark., I developed a great admiration for senators, both Republicans and Democrats, but most of all for the institution of Congress.Fifty years ago, congressional hearings were fewer than today, and members were often well-prepared. I sat on the Senate floor through debates that were real, with members challenging each other's views face-to-face. You learned something listening to them.In 1985, based on my experience as a Senate committee staffer and journalist watching floor action, I wrote an article for The Washington Post supporting gavel-to-gavel TV coverage of the Senate floor activity.What a mistake.With cameras trained on them, senators and House members now almost never confront each other face-to-face, facts vs. facts, any more. Great debates these days are seriatim speeches, often giving not only contradictory points of view but also contradictory facts.Congressional hearings have also become TV events. Members and witnesses often play to the cameras. When a controversial subject is the focus, more and more often individuals or groups hold demonstrations to have their moment on television.During Wednesday's court argument on DOMA, there were occasional chuckles in the audience based on a justice's remark or a lawyer's response, but no demonstrations, no one shouting and getting hustled out by security personnel.Cameras would change that. Today, there is audio, which television uses with sketches or still photos of the speaker. What's wrong with that?Put a camera in the Supreme Court, and you will have film clips based less on substance and more on theatrics. You will have attorneys and even justices -- aware of the broader audience -- shaping what they say and how they say it.Justice Clarence Thomas often leans back during arguments with his hands behind his head. That's a shot his critics would like to have. Justice Ruth Bader Ginsburg often talks with her head down, and sometimes while listening she appears to be sleeping. Get that shot.When Chief Justice John Roberts Jr. leaned forward Wednesday to question why President Barack Obama "doesn't have the courage of his convictions and execute not only the [DOMA] statute, but do it consistent with his view of the Constitution," did he look contemptuous? Make sure you use it.Outside the court Tuesday and Wednesday, there were hundreds of people trying to get on television, and many, including a dog, did. That's a part of our democracy in action.But can't we still preserve our democracy without exposing the court to those who would make a scene for the cameras?Let's not let them ruin the nation's last bastion for serious discussion of serious issues by serious people.Walter Pincus reports on intelligence, defense and foreign policy for The Washington Post.