Depending on the orientation of his body in his grave (was he buried? I don't know the relevant history and/or religious texts) and the position of his grave relative to Norway, isn't it possible that anything mean in that country would be said behind his back?
I've researched this and according to https://www.everplans.com/articles/muslim-funeral-traditions, Muslims are usually buried facing Mecca. Given that the burial place of the Prophet is roughly between Mecca and Norway, if he was buried facing Mecca, he would have his back turned to Norway.
Blasphemous implications aside, was the Prophet Muhammad buried facing Mecca?