There is no light side of the Force, but there is a dark side.
There's the Force, and an aspect of the Force that is called its "dark side". The dark side is a corruptive force, and denying that it is an actual thing is rather silly.
Well that does fit with the films and the books.
Like balancing between being healthy or stricken with cancer...
I know, I can't quite see it myself, but apparently Jolee Bindo could see a balance between the two in Kotor1, and for those people who want a Grey side to the force it has to be a maintained balance betwixt the two.