obscene
猥 centers on indecent or lewd behavior, with the core idea of obscenity. It describes things that are morally offensive in a sexual or crude way.
猥 combines the animal radical 犭 with 畏 (fear, awe). The exact historical development is uncertain, but the combination likely conveyed something base or indecent, perhaps originally associated with animalistic behavior.
A beast (犭) that inspires fear or awe (畏) because of its indecent behavior: imagine a lewd animal acting obscenely.
For ワイ, picture someone shouting 'Why?' in shock at the obscene scene: 'Why?' -> ワイ, as they recoil from the lewd beast.