That's a rather forced example. Unilateral channel closures always have a timelock — in practice, it's at least a day, and often up to a week. That’s the window during which a justice transaction can be confirmed. In your example, you're assuming there's a high volume of spam on the network. On top of that, the spam transactions have high fees — significantly above the average for non-spam transactions, which is a critical part of your assumption. So, it's possible that the justice transaction wouldn't get confirmed within a day. But that's still quite unlikely.

In reality, spam levels are low. And that's exactly what the relay policy is for — to keep it that way. 😎