Stupidity: Mr, Freeze and Poison Ivy join together and plan to cover Gotham in freezing temperatures and plants, with none of them ever considering in the slightest that plants don't survive freezing temperatures, despite both of them being scientists.
Suggested correction: Poison Ivy made super-plants that could survive the new ice age they were going to create. As for the fate of normal plants, though this is only really clarified in the novelization (and original script), Poison Ivy's god complex has (pun intended) grown to where she no longer cares about individual or existing plants, just playing out her fantasies of being "Mother Nature."
Stupidity: Batman blows up a rocket to avoid it crashing back to Gotham. You would've thought he would have more sense to detonate it whilst it was out of the earth's atmosphere So, basically, he has turned 1 falling object into hundred of falling objects. (01:11:15 - 01:11:50)
Suggested correction: Batman's bomb probably has a set time to go off, couldn't have it go off until it was higher. So he slapped it on immediately and went after Freeze. The rocket disintegrated in the explosion, making it harmless.
Completely ridiculous correction that contradicts what the movie itself shows. You literally see it explode right after Batman exits. There's no "set timer" outside of a couple-second delay.