God is pretty serious about that whole first and second commandment thing. There is only one God, first commandment, no idols, second commandment. In fact, in this chapter he says if anyone among you, whether they be prophets, or neighbors, or sons or daughters, or spouse, or father or mother, or anyone at all who might be telling people that there is a god other than the Almighty God, there is only one solution. Put them to death. We are even given a sequence of events on how to put them to death. You own hand shall kill them first, and then the town should stone them.
The priority that God places on us worshiping Him and Him alone cannot be overstated. Our God is an awesome God, He reigns and doesn’t take prisoners. I am also very, very grateful for our God as seen in Jesus Christ who ministers to the Samaritan woman (who worshiped other gods by the way) and treated her with tenderness and respect and as a result she and the entire village came to a saving knowledge of Jesus as the Messiah. You can find that story in John 4.
I prefer that approach to those who do not believe in God. Not a scorched earth approach, but rather a relational approach where you give them a chance to see the love of God.