In any case it's trivial to come up with such a definition that covers most cases. Doesn't matter if it doesn't cover some gray areas or 100% of it. Laws can be supplemented and ammended.
We don't have an all-encompassing definition of porn either, but we have legal definitions, and we have legal frameworks regarding it.
That's exactly the thing that matters when you're dealing with something where every loophole is going to have a caravan of trucks driving through it.
> We don't have an all-encompassing definition of porn either, but we have legal definitions, and we have legal frameworks regarding it.
You're picking the thing which is a hopeless disaster as your exemplar?