I think this is a dead end argument. We already have adequate definitions to regulate pornography. Poem can apply those to banning it, without having to re-litigate the legal framework we already accept.
In the US, the Supreme Court has developed and applied the Miller Test to determine whether something is obscene given the circumstances of any particular case. If a work is not obscene in the context in which it appears, whether or not it's "porn" by someone's definition, then it's protected by the First Amendment and cannot be banned. Poem is not satisfied with the Miller Test and claims it needs "tweaking." Until he specifies exactly how, he has zero workable definitions to apply as far as US law is concerned. If he wants to limit discussion to non US countries, that won't be an issue (though good luck getting e.g. Japan to fall in line), but so far his wishes haven't been less than global.