Stupidity: Given Louise's character, it makes no sense at all for her to leave Thelma in charge of the money. She's known Thelma for years, and knows fully well how flaky Thelma is. And Louise is shown as a person who lives by "If you want something right, you've gotta do it yourself". She's responsible, perhaps even uptight, at that point in the movie. So it defies everything about her character that she would let Thelma guard the money - it smells like a device set up just to allow the money to be stolen.
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: Instead of breaking into Gordo's house, covering all the furniture in one room with sheets/thin blankets, and waiting for Gordo to return home in order to kill him via a "dramatic re-enactment" (in an adjacent room which was not shown to the audience), Bill could have taken Gordo anywhere to avoid getting caught or calling the police on himself. Had Bill taken Gordo to his already-"wrapped" motel room, he had enough injuries after the fight to claim self-defense against an intruder. (01:43:20)
Stupidity: The trail of yarn supposedly unveiled by the cat - besides the 'small' detail that comes down with perfect timing that the murderer couldn't have planned - has also a pattern that is only meant to imitate what happens when a cat plays with a ball of yarn; in reality it couldn't have such a precise trail, and yet retaining loops that wide and neat. (01:00:00)
Stupidity: Molly was being hunted and didn't know if she could trust Rayburn when he encountered her. Rayburn told Molly that he wanted to help, wouldn't hurt her, put a blanket around her, and even carried her in the woods for some distance. When he put her on the ground (along with his backpack and rifle) to go find the rope to open the pitfall doors and had his back turned, Molly got out from under the blanket and hid nearby. Rayburn quickly found Molly, and Molly made a lame attempt at attacking him with some kind of club. The next day when Rayburn and Molly were in Rayburn's house and her hunter showed up and attacked Rayburn, Molly grabbed Rayburn's rifle and fired several shots at the hunter. Molly obviously knew how to use a rifle, so it was asinine for her to have hidden from Rayburn the previously night without taking his rifle (or the blanket). (00:36:22)
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: In the bar scene, Jack gets into a fight with a guy he busted a few years back, then Reggie turns to the bartender and asks for a gun. The bartender hardly hesitates and hands it over. There is just simply no scenario where a bartender would hand a loaded gun to a patron they had just met.
Stupidity: Just after Ricky has beaten up Tarzan, the warden has the ceiling of the cell Ricky is trapped in lowered in an attempt to crush him. However, earlier in the scene, Tarzan made a huge hole in the wall of the cell to get into it. The hole in the wall is even visible in the background when the ceiling begins to lower. Ricky could have simply run out of the hole in the wall to get out, rather than try to hold the ceiling up with his bare hands. (01:02:48)
Stupidity: The end fell apart. It took convincing to get the police at the picnic area; however, while Jack was cracking up, they just left alone with his gun. After the stakeout was a bust, why didn't the police just question the girl: "Who told you to come here? Who was to meet you here?" Also, they police see a smashed black station-wagon. Was there no connection to the previous child's drawing?
Stupidity: In the original novel, the attempt on Mrs. Doyle at the temples was made rolling a boulder off a cliff. In this adaptation, the culprit is said to 'dislodge' a large stone from the temple; you can however see that the stone is already dislodged and sticks out from its place on the pillar, and he had no way to know that the Doyles would be in that particular spot, making this attempt to Linnet's life rather nonsensical (requiring also herculean strength, no pun intended). (00:47:40 - 01:39:30)
Stupidity: The metro police officer (and co-conspirator) went to the old cement factory where the other bank robbers were. Since the police officer (accomplice) wanted the money and did not want other police officers to be nearby, he called 911 and made an anonymous false report stating he spotted the person police were looking for and misdirected them further away. Maybe a good idea, but he made this call using his own cell phone. (01:12:20)
Stupidity: In the film climax, Cassie tells Justin to put his gun on the floor and walk over to her. This he does but it gives Richard the chance to grab the gun, so we can have the usual daft Hollywood ending. Why didn't she simply tell him to kick the gun over to her first to void this?
Stupidity: When the police turn up the first time the mother lies to them to get them to go away but the burglars can't hear the conversation. She could have told them exactly what was happening and that she had to make it look like she'd got rid of them. She could have then smashed all the cameras and just let them in.
Suggested correction: This was a character decision, and a completely understandable one. Her daughter was being held hostage in the panic room. She decided to cooperate with their demands for the safety of her daughter. Your idea is a solid one, but she simply did not think of it in her state of mind. She opted to get rid of the police, and her decision is not a movie mistake.
Stupidity: When Alice opens the door for the dumbwaiter, how did she not see the bottom of the elevator was removed when she was looking right at it? She even realised it was missing as she was getting in, but she still let go and fell to the basement.
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: Dirk squeezed a long stream of lighter fluid onto the pile of Mario's clothes, then saw a necklace, which he removed (and potentially got lighter fluid on his hand while doing so). Instead of tossing a match from a safe (r) distance, Dirk crouched next to the saturated clothes and held a match near the bottom of the pile, risking burning himself. (00:06:40 - 00:07:21)