The right to criticize carries with it a responsibility— to study the facts, to be fully informed . . . So I would emphasize that debate and discussion must be based on facts, not merely rhetoric. And those who would criticize have a responsibility— to listen, to engage in a two-way discussion. Over and over throughout our history, both in this country and elsewhere, we have seen that it is the extremists who do not permit others to talk, who refuse to engage in discussion. It is the Communists and the radical right whose polemics will not stand up to the force of logic inherent in reasoned discussion. So if our young people—or anyone else for that matter wish to criticize, I defend that. But they must also be willing to listen while others speak; and they must be willing to have their views tested in the market-place of ideas.