I can't figure out if you are serious or not, because that is such a naive statement. But either way, obligatory PG essay link in case you are unfamiliar.
It would be helpful if you could enumerate the ways in which his/her statement was naive. It seems to be a relatively logical conclusion that being told or influenced not to say something is restrictive of innate freedom of speech, no matter how seemingly innocuous a reasoning established social or cultural norms are (ie. don't criticize the recently deceased, it's tactless).
It was naive in not seeming to grasp that there are many senses of "can't" and "freedom," and that the sentence could be either true or false depending on which you mean.
You're right, it is a very naive statement. But it's also a very serious one; the freedom to speak one's mind is the entire topic of this discussion, and I am of the opinion that freedom of speech is so important that it should be a reserved right, inalienable and indelible.
That was a good essay. I liked it. What conclusions did you want me to draw from it?
Much like brlewis said in his response to the GP, no one said that RMS can't say what he thinks: he will not be hauled away to labor camp for saying it. However, the other topic of this discussion is that the rest of the community has the freedom to pass judgment on tactless people like RMS, which is exactly what's happening.