The free-speech argument kind of loses its luster when you send something without your name attached.
Maybe you're not from the US, but the US has a legal tradition of strong protections for anonymous and pseudonymous speech. The Federalist Papers, which were a key part of the political discourse leading to the existence of the US, were published anonymously. So maybe what you say is true in Ukraine or China or Myanmar or wherever you're from, but it's certainly not true in the US.
I am from the United States - anonymous and pseudonymous protections wouldn't apply to this case of slander/libel and/or criminal harassment. Anonymously outing someone against their will does not fall under the same protections that critiquing an unfair government does.
I didn't mean to imply that all anonymous talk is without protection, just that in this specific case, the defendant in question would probably have a very difficult time making a successful free speech argument.
Maybe you're not from the US, but the US has a legal tradition of strong protections for anonymous and pseudonymous speech. The Federalist Papers, which were a key part of the political discourse leading to the existence of the US, were published anonymously. So maybe what you say is true in Ukraine or China or Myanmar or wherever you're from, but it's certainly not true in the US.