You can theorize that the first amendment doesn't protect speech that is intended to arouse, you can even invent a "cognitive test" but neither are supported by a textual or historical analysis of the 1st amendment. Further even if you could demonstrably prove without a shadow of a doubt that it is not protected speech, that does not give government the legitimate power to ban it.
Please note that your argument is directly analogous to that of the liberals anti 2nd amendment arguments of "The founders never intended the 2nd amendment to protect assault weapons". Further it forwards the premise that government has any power except for those specifically curtailed, which while wildly popular amongst democrats, turns constitution principle on it's head.
The only legal way to ban pornography is via constitutional amendment and even that would be dubious considering the 1st amendment which does not grant a right but recognizes a natural right.
OTOH, porn was restricted in the USA for many decades, without, I think, deleterious results.
The Icelanders will be facing identical questions. It will be interesting to see how they deal with it.