Sure. But there's a process.

1. Patience.
2. Send prophets to try to correct behaviour.
3. More patience.
4. More prophets.
5. Patience and prophets, over and over.
6. OK fine, you won't have it any other way. Judgment.

We see prophets actually work. Jonah didn't want to go to Nineveh, he wanted to jump straight to 6, but God had other plans. When God finally got him to go to Nineveh, the people listened, repented, and judgment was avoided. The reason Jonah didn't want to go is that he thought there was a strong possibility of that outcome and he wanted the Ninevites to suffer judgment.

Hmm.. just noticed the sidebar. This defence of the OT probably violates Rule 1. Forget the above, yay God, what a dick, punishing people for being evil!