Would that such an "intimidating" sign could actually protect us. Jesus says when we pray we should ask to be delivered from evil.
"Heavenly Father, you are the creator and sustainer of the universe. You sustain us — body, soul, mind and spirit — day by day, moment by moment. You alone deliver us from evil. Protect us today from evil — especially the evil in our own heart — and fill us with the Holy Spirit, that we might please you more and more each day."