To be fair, dark type is called "evil type" in Japanese, so I'm not sure a dark vs light typing would translate well. Especially since fairy and fighting types pretty much cover the light concept of the "darkness vs light" trope.

Fairy type pokemon often have angelic+magical traits/concepts & are rarely truly "bad". Fighting types are often given traits of wrestlers & classical heroes, with a "defeat the bad guys & do good" concept. They are also almost always portrayed as virtuous & just. They are also both super-effective against dark types.

So those types together sum up the general "light" side. Dark type & ghost type sum up the general "darkness" side. That's how I always saw it, at least.