Paul wrote, 'But the natural man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know them, because they are spiritually discerned' (1 Corinthians 2:14). Those who have never experienced the Holy Spirit are not in a position to judge those of us who have. They cannot know the things of the Spirit because they do not have the light of the Spirit. This is why, to many of them, all the shouting and speaking in tongues in simply foolishness.
We must not be judgmental toward these people but rather pray that God would enlighten them. Many who at one point in their life laughed at the pentecostal experience are now shouting and speaking in tonguies themselves!