Agreed.
Hypothetically, if a SOPA bill did in fact pass and go into effect, law enforcement would more than likely shut down the pirating side of things. From my view, fanart and fanfics, or even gifs are probably safe.
First off, if the only thing between you and criminal prosecution is prosecutorial discretion, then I question how safe you should feel. When prosecutors change, so do their policies. Realistically, those prosecutors have a finite amount of resources and will not prosecutor small fries when it's more efficient to make examples out of the bigger ones. Why prosecute "Lid" when you can nail ff.net as a whole? But if a prosecutor becomes interested in you what would stop him or her from going after you?
Second, fanfics and fanarts are violate current law. I don't know that SOPA did anything to change what is copyrighted material, so much as it expanded the criminal enforcement side. There are two ways of enforcing violations Criminal and Civil. Civil is the primary method used as the criminal portion is pretty narrow. Fanfics and Fanarts are blatant derivative works: something that it protected by current copyright law.
In other words, we can all be sued for every fanfic or fanart we create. Most creators allow such fanworks to exist and simply choose not to pursue it. But they are under no obligation to do so.