Scott Peck is a very angry man and something of a sociopath himself. It is not surprising that he would be sucked in by Malachi Martin. In "The People of the Lie" he acts as if he alone deserves credit for discovering the fact of the presence of evil in the modern world. Duh.
In an interview with Bernard Janzen, Fr. Martin speaks of a Protestant man, who he does not name, but says that he is well known, who requested to be instructed in exorcisms. Fr. Martin recounts that he warned this man not to try an exorcism without an experienced Catholic priest because of the danger, however the man did not listen. Fr. Martin goes on to say that as a result of this man doing this on his own, this man became possessed himself. I've often wondered to whom Fr. Martin was referring.