>>44570784>>44568566 that's why.It's not evil but it has power over evil forces (or to sense them, anyway). It fits the persona and aesthetic of an evil thing, but uses that affiliation for noble causes.
Absol's that really shady intimidating guy you meet in a tavern, covered in scars and with fierce eyes and a low, gritty voice. He seems like he is something to be feared and wary of, but in reality he's only there to protect you from things that would hurt you. Absol is fulfilling a role within Pokémon's cast, that being of the hero who takes all the appearance of a villain.
And yeah, the yin yang thing points to all this being intentional. Not bad, just got some bad powers.