I've seen this argument (if linking to wikipedia qualifies as one) so many times, and it always strikes me that those who cite it often have either not read, or completely miss the point Karl Popper was trying to make. He goes so far as to even say: "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 unwise." I am quite sick of the usage of the paradox of tolerance being used as an attack against freedom of speech.