In my book I recall when Bishop Fulton Sheen warned us in his popular retelling of the life of Christ, The Eternal Galilean: "Do not mock the Gospels and say there is no Satan. Evil is too real in the world to say that. Do not say the idea of Satan is dead and gone. Satan never gains so many cohorts as when, in his shrewdness, he spreads the rumor that he is long since dead." Such an attitude only leaves the devil freer than he would otherwise be to work to gain souls for hell. “I am who am not.”
Fr. Longenecker has weighed in on this here.