There is heat in God's relationship with His people. Within the Ten Commandments, in the second commandment, He says, "For the LORD your God is a jealous God." What is jealousy? It is a passionate intolerance, even a hostility, toward a rival. It is also defined as vigilance in guarding a possession.
In this passage, God is having a passionate reaction against a rival, idolatry. God will not permit idolatry without reacting because idolatry promotes divided loyalties. We are His, and He does not choose to share us with anybody or anything else.