I mean, really. Dark types simply cannot be evil.
I mean, it seemed to be canon that there is no such thing as an evil pokemon (It was mentioned countless times in the Anime that there isn't an evil pokemon. And I THINK that it was mentioned in the games as well, or at the very least implied.). If there were evil pokemon, then Ekans and Koffing lied to Meowth in regards to their being no evil pokemon. Plus, many of the "Dark" types were portrayed to be somewhat misunderstood and all that.
For those of you who will try to counter me, I just want to give counterevidence to your counterexamples.
One. Meowth. Ok, yes, he may have tried to refute their beliefs in regards to their being no evil pokemon by saying he himself is evil, but I think that deep down he wasn't evil (Heck, his reaction to not being followed didn't seem close to evil, since if he really felt he was evil, he would have tortured Ekans and Koffing to follow him even though they won't obey anyone but their masters, especially not a pokemon of their level.), Plus, he seemed genuinely horrified whenever several pokemon are being harmed (for instance, when Giovanni was going to torture the cloned pokemon, as well as Ash and Co., and especially Mewtwo in "Mewtwo Returns", he could have easily not given a care about it. But Meowth was genuinely horrified by his Boss's actions, even going AS FAR as to go against his boss and trying to save Mewtwo, and all the other Pokemon.)
Two. the snack thief Teddiursa. Look, it may have stolen food, but it most likely needed it to survive (heck, it could have been smiling because it finally has something to eat.), also, about the placing the blame on some other pokemon, how is that any different compared to how Pikachu allowed Porygon to become the scapegoat of the little stint that Pika was responsible for? should we label it as an "evil" Pokemon as well?
Three. the Ancient Mew card. Look, the card shouldn't really count since the only "hint" it gave to it being "evil" was the way the question was worded. If we reworded it, it most likely won't have been labeled as evil.
Four. Spiritomb. Look, it was angered that it was sealed away, and most likely never knew how to control it's power. Plus, many pokemon have attacked civilizations and were still labeled as a non-evil pokemon. Take Rayquaza, for example. I mean, it DID attack LaRousse city (I know it was trying to defeat Deoxys because it percieved it as a threat, but it's actions placed innocent bystandards in grave danger.), and yet I don't recall anyone labeling it as an evil pokemon. Heck, MOST of the Legendaries have harmed society as a whole, should we label ALL of them as being evil as well?
Anyways, that's all for now.