First of all, you've just blindly assumed this. Secondly, what you've said for both situations are completely different. You've said what the gore images may represent, but not what it causes people to do and you've said what the nude images may cause young people to do, ignoring what the images represent.
Yes, gore may help bring harsh reality home, but that doesn't mean it will change peoples opinions just like naked men and women won't make people sext each other. Hell, it will make it less likely as they have pictures of naked men and women already.
Who decides whats obscene? It may seem obvious, but in certain situations what could be perfectly fine in one persons view is completely offensive to another.