There are many ways people use the Lord’s name in vain, some use it as a curse word and others live in a way that deny they know Christ at all even though they call themselves Christians, but others do the third:
Some people use the name of Jesus as a magic word. Yet if they do not personally follow Jesus or have faith in him, they also do not personally have the power of Jesus living in them by faith. They are not realizing it that saying that name without knowing him personally is as silly as an unarmed civilian who plays policeman and tries to arrest a drug dealer- without having powers vested in him by the state.
Police have authority and firepower, and yes even then they must follow the laws. A Christ follower should let themselves be fully governed by the Law of Christ and the Word of God. To act carelessly with the forces of darkness is yes indeed as silly as a vigilante civilian trying to fight criminals when all he has on is a Spiderman outfit.