Hah, I love massively necro'd posts.
Anyway, as I am finishing up my first Imp now after several pubs, I cannot see any way someone could argue the Empire are not the bad guys. Every time you choose a dark side option on pub people act horrified and say you are a monster. Pretty much every time you choose a light side option as an Imp you are basically ridiculed and called weak or stupid unless you can justify it with some sort of alternative reasoning. Half of the Empire story arcs are basically to do evil for evil's sake, or at least for very minimal advantage. There might be bad apples in the Republic and there might be some non-monsters in the Empire, but both are the exception from everything I have seen in this game (and most of the bad apple pubs can actually be defied/turned in on those missions).