Kerry made the remarks at a school in Berlin while defending America's freedom of speech and religion, Reuters reported.
"People have sometimes wondered about why our Supreme Court allows one group or another to march in a parade even though it's the most provocative thing in the world and they carry signs that are an insult to one group or another," he said.
"The reason is, that's freedom, freedom of speech. In America, you have a right to be stupid if you want to be," he added to laughter. "And you have a right to be disconnected to somebody else if you want to be.
"And we tolerate it. We somehow make it through that. Now, I think that's a virtue. I think that's something worth fighting for," Kerry said.
The remark comes one day after the former Massachusetts senator made up the name of a country -- morphing Kyrgyzstan and Kazakhstan into “Kyrzakhstan" -- while speaking in London, the Washington Times reported.
Later Tuesday, the former senator delighted a packed crowd at an Internet cafe with a few sentences of passable German, and told them stories of his boyhood in Berlin in 1954, Politico reported.