>>39502616Dunnk how young you are, but Pokemania had a big "this is the work of Satan" stigma to it back in the late 90's and early 2000's. When gold and silver released, that was still a live criticism. Localizing it as "evil" would have opened up a huge can of worms. Dark at least comes off as something more abstract.
Also fighting is the "light" type. Dark type moves are like dirty fighting moves. Sucker punch, bite, beat up, etc. It's like fighting moves but the unsportsman kinds. Its why the swords of justice are fighting types.