I believe Rod Dreher is Eastern Orthodox. I don't share his belief in Purgatorial punishment.
Evidence of the existence of ghosts disproves atheism inasmuch as atheists typically deny the afterlife. Most atheists, at least Western atheists (in contrast to Buddhist), are physicalists.
Oddly enough, many Christians agree with atheists regarding the nonexistence of ghosts even though Christians traditionally believe in the immortal soul, which is separable from the body.
Although I think death seals our eternal fate (I reject postmortem salvation), that of itself doesn't imply that there can be no contact between the living and the dead (or the damned). Of course, necromancy is forbidden, but that doesn't mean contact is impossible. And there's an elementary moral distinction between soliciting initiating contact with the dead, which is prohibited, and having the dead initiate contact.