The weird thing is, just a short time later, after the visit to Rumple in his prison cell, Charming speaks in favor of trusting Rumple: “If you believed him about the curse then you must believe him about our child. She will be the savior.”
So we go from Rumple helping Charming and Snow reunite (and thus helping Charming save Snow’s life), to the “scourge” statement and the deception leading to imprisonment, to “believe him.” Either we’re missing some major plot points in between or Charming is showing signs of Davidness.