You know there is no such thing as the world police or something of that sort.

If the perpetrator is in another country / jurisdiction it is virtually impossible to prosecute let alone sentence.

It is 100% regulatory problem in this case. You just cannot allow this content to be generated and distributed in the public domain by anonymous users. It has nothing to do with free speech but with civility and common understanding of what is morally wrong / right.

Obviously you cannot prevent this in private forums unless it is made illegal which is a completely different problem that requires a very different solution.