As John says, the concept of good and bad is largely determined by one’s tribal affiliations, and much Sci Fi is merely a reflection of the time they were written in. The fascist future of Starship Troopers might as well just substitute the words Jap’s and Square heads for Skinnies and Bugs, and James Lucas never made it a particular secret that the Empire in the original Star Wars was based on the US in Vietnam, before it morphed into a hybrid of Nazi Germany and the USSR.
Evil, as random and arbitrary cruelty and a delight in the suffering of others, is probably easier to determine than “bad” but as in all human relations, there are shades of grey. All conflicts, be they military or social, which involve the redistribution of wealth and power will have winners and losers, and so be good or bad depending where you are. The violence inherent in the system is just more obvious in some forms political organisation than others. As noted above, Sci Fi is often more nuanced than the bile we see in our daily media, who are the baddies in Ian Banks universe?
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke