Earlier quoted context omitted.
No, it's not. Freedom of speech doesn't cover slander/libel. Freedom of speech means government can't put you in a cage for your expressed ideas (with few exceptions, like yelling fire in a theater).
> like yelling fire in a theater I hate that this example is always used. Yelling fire in a theator for a laugh isn't "expressing ideas". It's a kind of social fraud: in some sense we depend on each other to make society work and someone shouting that our lives are in danger when they are not is violating this trust. Not by expressing some philosophical ideal but by exclaiming something they know to be false.
There's nothing about the constitutional idea of free speech that says it has to be of philosophical value or true.