Q. The Bible says that God is a "jealous God." Doesn't this mean He is somehow imperfect? If a man knows that his wife is having an affair, and he's not hurt by that, that's not normal. And this is how God means He is a jealous God.
A normal, even godly, response is to be grieved by a wandering spouse. Now the defect of jealousy is when a person is being faithful, and their spouse is constantly mistrusting them. That's actually a kind of phobia.
People are often jealous and distrustful without cause. And I've seen this destroy marriages and otherwise positive relationships. That is a fault, a defect in human nature. So there are two sides of the jealousy coin. On one side there's an appropriate, normal jealousy from love. The other side is an abnormal jealousy from fear.
In a sense, the Lord has married the church He has a right to be jealous if we decide to worship other gods when we have already accepted Him as head of our house. We even take His name. And we take His name in vain when we call ourselves Christians and worship other Gods. He wants our loyalty because we have promised it to Him through repentance and baptism.
But the other form of jealousy is when a man follows his wife around and secretly checks her mail. That's a sickness.