"What comes out of the mouth proceeds from the heart, and this defiles a person. For out of the heart come evil thoughts..."
The demons immediately recognized Jesus's authority and begged for mercy, while the townspeople only saw property damage (lost pigs) and asked Jesus to leave their region.
Those who witnessed miracles and heard His teachings later joined the mob shouting for His crucifixion - a pattern of spiritual blindness despite physical sight.
The "religious" humans, renowned for their ritual purity and knowledge of Scripture, possessed worse spiritual perception than demons. The Pharisees failed to recognize God standing before them, while demons immediately identified and submitted to Him.
Individuals who struggle to perceive spiritual warfare or God's presence might actually have less spiritual awareness than the demons they deny exist. Our outward expressions reveal our inner state - what proceeds from our mouths reveals the condition of our hearts.
Demons spoke truth about Jesus; religious leaders spoke lies.
Their words exposed their respective heart conditions.