As a note, we are canonblind! However, since these people aren't technically 'people' and don't have... well, souls or general personhood, then killing them may not count toward a corruption-esque game mechanic, unless the EXP mechanic was more about the moral decision of killing vs the type of creature being killed.

All of that is a bit complicated, but ultimately it's totally up to you guys! You're free to treat these ghosts however you want in terms of EXP.