Stupidity: All the mutants on the island need Magneto at the last second to take control of the missiles so they don't land and explode. Why didn't Azazel just teleport everyone off the island?
Suggested correction: Given the situation, there was probably very little time to come up with a plan like this. The missiles were flying towards them extremely quickly, and there would have been nowhere near enough time to band every single person together for Azazel to teleport them all out of there in just a few seconds.
There was plenty of time. He could have taken 5 at a time down the Beach 3 miles and came back for the rest. Earlier in the movie he was moving so fast men were falling from the sky at nearly the same time and he was teleporting them one at a time.
Stupidity: When the crew go to New York they are in the back of a fish truck carrying fish. There's no need for them to do that. So long as the truck looks normal outside to keep their cover, they could have the inside kitted out any way they want. When they get to the fish factory they open up the warehouse in front of the workers to reveal the cars, so the workers are in on it being a front - it makes no sense to actually have fish in the back of the truck.
Stupidity: If Guerrero had limited money and wanted to be sure to blow up the plane over water, he certainly could have bought a ticket to a much cheaper destination than Rome, such as a Caribbean island.
Suggested correction: "The North Atlantic leaves no traces." He wanted to down the plane where recovery and investigation would have been practically impossible.
Stupidity: The Nostromo essentially is a detachable ship attached to a mining platform. After it returns and docks with the platform, much of the movie occurs in the platform section and not the Nostromo itself. The supposed reason they can't just blow up the ship is that the shuttle can't fit everyone. Why couldn't they just lure the alien into the platform, seal the ship, and then use the ship itself to escape? They could then blow up the platform to kill the alien.
Suggested correction: Dallas tries to flush the alien out of the air ducts and is presumably killed. Lambert suggests fleeing in the shuttle, but it cannot support 4 people. Ripley decides to continue with Dallas' plan, but before she does so, accesses Mother and finds out Ash was ordered to help bring the alien back alive. When confronting Ash with this, Ash attacks Ripley and is revealed as an android. The survivors then decide to go with Lambert's plan because now there are only 3 people. There is no error here.
Stupidity: A movie always needs extra conflict, but Julie's reasoning for walking out on Marcus and Mike is one of the dumbest. "If his wife can find us, I'm a LOT better off on my own." What sort of logic is that? She's the wife of his best friend. Of course she knows where he lives. (01:32:45)
Stupidity: The system prompts a message for the bank clerk saying that the subject trying to withdraw cash is armed and dangerous and to alert the local authorities. It also alerts the 'subjects' themselves though, since it beeps a persistent alarm tone! Seems a rather poorly designed system that would endanger the staff. (00:50:10)
Stupidity: Despite being assaulted by an intruder that she managed to temporarily fend off, the female neighbor takes forever to say something when she calls the police, which is just enough time for the villain to regain his senses and attack her with a huge drill.
Stupidity: Bond has been shot at and hunted down by armed men and dogs. He must conclude his life is in danger, and yet after Bond despatches the armed man in the creek who is carrying a British Sten submachine gun, he fails to pickup the weapon which has far superior firepower to his small calibre hand gun. Had he done, so he may well have saved Quarrel and avoided capture.
Stupidity: When Will Smith and Gene Hackman are running through the railroad yard. Gene calls Will by his real name, "Will" and not by his character's name "Robert."
Suggested correction: You could be a little bit more specific, but I don't hear him say "Will" at any point during that run.
Stupidity: When the duke approaches the wall at the end, Snake dives on him and briefly knocks him out. Snake could have easily grabbed his gun back and left the duke unarmed (or even just killed the duke there and then), but just gets up and runs, leaving it with him.
Stupidity: When Bobbi Jo sees Ash's severed possessed hand holding her hand, she freaks out and runs out of the cabin and then gets killed by possessed trees. While it's certainly natural for her to be terrified, why would she run AWAY from where all her friends are and go off by herself?
Suggested correction: She is a civilian in a blind panic, and even people with actual training have done dumber in panics (e.g., choking firefighters run away from other firefighters who could help them). She also has no idea how dangerous the woods are at this point; she walked to the cabin just fine and only saw scary things inside it, so she thinks she'll be fine if she just runs from the cabin.
Stupidity: Carl buries the case with the money in a field by a fence. He looks at the fence line and wonders how he is going to be able to find the spot when he returns. He plants an orange ice scrapper to mark the spot. The scrapper is only 6-8 inches, but it's the middle of winter in Minnesota. The scrapper will be buried by snow. He should have marked the spot by tying something on the fence. (01:18:26)
Stupidity: At the end Vince fires a grappling hook at the passenger seat of the truck then attaches the other end to himself, all the truck driver has to do now is hit the brakes and Vince would be dead under the truck or dragged along the road.
Suggested correction: In point of fact, the truck driver does slam on his brakes; but, defying physics, Vince is catapulted around the right side of the truck to the passenger door.
Stupidity: After Dan confesses his affair to his wife, he never thinks about bringing the tape Alex had sent him to the police. This would have been proof beyond a reasonable doubt of her mental instability and harassment of him, and she would have been immediately sought out and likely committed to an institution, and both of the film's endings wouldn't had to happen.
Stupidity: After the Defranco "assassination" Rollie learns he is a target and survives two attempts on his life. But instead of leaving town or finding somewhere else to hide for the night, he spends the night in his own apartment (even though he was well aware the killers knew where he lived). As a result, his girlfriend is killed and he barely escapes alive.
Stupidity: When Marlene deduces "Peyton" as being Dr. Mott's widow, she drives to the house to warn Claire. When she arrives, she foolishly decides to confront Mrs. Mott with this knowledge right to her face and demands to know where Claire is... which ends up with her being killed in Claire's place. Instead, she simply should have waited or looked for Claire, rather than confronting "Peyton."
Stupidity: After Jack is found not guilty, you would think the first thing he would do is to get rid of the typewriter he used to send the notes to Teddy to manipulate her into winning the case for him, especially when she is sleeping with him at his home. Not to even mention the fact he hid the typewriter in an unsecure manner in a closet behind a stack of towels, a place where it would very easily be found. This foolish mistake exposed the truth to Teddy and cost him his "freedom."
Stupidity: The first time they see the bad guy in the Land Rover, Morgan has him in his sights but can't shoot, as he doesn't want to kill him. Clearly, the obvious thing to do is to shoot the car tires, but he doesn't and lets him drive off.
Suggested correction: Shooting out car tires is not an actual effective strategy to get a vehicle to stop. A 9mm bullet simply doesn't cause enough damage to a tire to get it to go flat immediately. It causes similar damage as running over a nail. It is a movie cliche, similar to using a gun to shoot out a lock or a rope, it just doesn't happen in real life.