I'm not saying Jonah was right, but I don't think calling him a jerk tells the full account. Or even calling him a racist bigot. It's more complex than that.
Jonah's people were pretty much annihilated by the Assyrians in or at least by 722 BC. It wasn't a pretty sight. Assyrians used to skin their enemies alive, impale people on poles, and lead their slaves around with fish-hooks through their lips attached to ropes or chains, and otherwise, completely brutalize their conquered subjects.
https://pdfs.semanticscholar.org/f4a...d13832cd46.pdf
So, if you are a prophet, and you know the Word of God so far written up to that point, you know the LORD is good and His mercy endures forever, and you know that His prophets of old have ever spoken of His great grace and steadfast love, even for heathens.
So, deep down, you know that God could very well spare the heathen Ninevites, and grant them mercy in repentance, because that's something God has been doing with your people since day one, even when your people have acted worse than the heathens surrounding your nation.
So, you know it down to the core of your being, but you just can't bring yourself to desire to see it come to pass, because you know how horrifically your people have suffered under their reign of terror.
Put yourself in his place for a moment. If someone invaded your home, slaughtered as many as they could, raped and pillaged across the land, brutalized your women, your children, your elderly, enslaved however many they didn't outright kill, and took them all away never to be seen or heard from again, and then, sometime after that, God speaks to you and tells you to go and preach to that invading force because He desires to save them from their wickedness: that's Jonah.
And, you could even scale back all of that, and just speak to a home intruder that murders half your family and kidnaps your children, or some other terrible, but closely related crime, then imagine that God tells you to go and visit the perpetrator in prison and share the Gospel with them.
Can you forgive such atrocities so easily and just go and be a saint? If not, does that make you a jerk? A racist bigot? Not at all. It makes you someone so hurt and enraged and inflamed with feelings of hatred, that getting past all of that requires a sovereign, miraculous work of the Holy Spirit, something Jonah wasn't prepared to experience.
The story, therefore, is designed to show us that even though we might be God's people, we sometimes don't understand or refuse to comprehend, the lengths God will go to to save His creation, even when they are at their most vile. So, Jonah teaches us that we must learn to be like God, to forgive the worst humanity has to throw at us, to care more for lost, corrupted, despicable, horrible humans, than our own petty concerns of comfort and religiosity. That even our worst enemies can still repent, while they live, and that their eternal life is more important than the pain or hurt they've caused us.
Because if we don't, there's nothing left for us but being swallowed by Sheol at the bottom of the ocean.