>>38385234I think it's because, back in Gen I, Poison was basically pulling double duty as the 'evil' type with how it was associated with the shadier characters like Koga, Agatha and Team Rocket. Psychic, meanwhile, could be considered a 'holy' or 'sacred' type, thus giving it the ability to banish Poison-types.
It's probably more a case of 'mind over matter' now that Psychic's been nerfed and Dark's become the de-facto 'evil' type, but it's interesting how a lot of the oddities with types have their roots in Gen I giving them multiple connotations.
