In this formulation, I do not imply, for instance, that we should always suppress the utterance of intolerant philosophies; as long as we can counter them by rational argument and keep them in check by public opinion, suppression would certainly be most unwise.

What form would the "utterance of intolerant philosophies" take, which can be countered by "rational argument" and kept in check by "public opinion?"

Did you actually read the the comment posted or simply scan it once for the word "speech?"

Utterance means speech.