"Freedom to Speak" is the way to say "Freedom of Speech" which makes more sense because it encourages people to speak more than when that right and freedom are called the "Freedom of Speech."
"Freedom of Speech" is a way of wording the "freedom to speak" in a way that distances the speaker(s) from the act. Humans do not "speech," they speak and can give a "speech." Calling that freedom the "Freedom to Speak" encourages people to speak more often and for longer swaths of time than when it is called the "Freedom of Speech." It is time to start using the expression which encourages Americans to SPEAK UP more. " God is in the details."
by but for October 29, 2017