
Stupidity: I won't begrudge Father Lamont for instinctively grabbing for the first thing in reach to try to smother the box on fire (even if it is a pair of wooden crutches), but you'd think at some point he'd notice that he's just spreading the fire and making it much, much worse, but he keeps at it until the doctor finally returns with the extinguisher.

Stupidity: When Amy tries to use the security cameras at Desi's house to make it look like he raped her, wouldn't the cops be curious as to why there was just one little scene - and not 30 days worth of footage? Wouldn't they question what happened to the rest of the footage (showing her being looked after by Desi and living comfortably), and why that little bit showing her crawling on the ground was left undeleted. Also she tied lace around her hands. Anyone could break material like that if they tried hard enough. Why would Desi risk that?

Stupidity: Denny removed a tray of chicken/capons from the oven, set it on the counter, cut off a piece from one chicken and threw it to Enzo (who caught it in his mouth). If the meat had just been removed from the oven, it would have been too hot to give to a dog and Enzo could have burned his mouth/tongue. (00:51:25)

Stupidity: Why would Stanley say the shoes fell out of the sky? It happened under a bridge. Any normal person would instantly realise someone threw them off the bridge.
Suggested correction: It's an idiom/expression. When something turns up out of nowhere, we say "it came/fell from the sky." In fact, Mr. Sir says this to Stanley when he finds Stanley with his empty bag of sunflower seeds, "Where did this come from? Did it fall from the sky?" Obviously a sarcastic way of saying, "it didn't get there by itself, someone put it there." So the shoes obviously fell from the bridge and Stanley knows this because Zero refers to the bridge later in the movie.

Stupidity: When Amy heard Luce coming toward the kitchen, she "hid" his school paper and bag of fireworks in a kitchen cupboard, apparently while knowing Luce would be doing the dishes (and putting them away in the cupboards). Amy and Peter were on the patio (with the door open) just outside the kitchen when Luce was doing the dishes yet Amy made no attempt to prevent Luce from finding his paper and bag of fireworks (which he did). (00:16:20 - 00:21:00)

Stupidity: There is no way Mr. Mertyle did not hear the fence in his backyard crash to the ground; there's also a likely chance he could hear his dog crying and Smalls saying the dog is hurt. Even if he could ignore the sounds of other attempts to try to get the ball back; with the fence coming down where his dog lives and the chances of an injured pet it seems far too unlikely he wouldn't have rushed straight to the backyard hearing this.

Stupidity: The protagonist knocks at every door, humiliates himself, losing any hope of getting his dream job, jumps through all sorts of hoops to get a court order to save Crawford's wife, but somehow, once he gets it, he has to drive through LA and physically get to the hospital room where euthanasia will be performed, because he couldn't be bothered to phone the hospital to tell them about the court order or talk to someone in the lobby.

Stupidity: Matt told Joey they could not check on the guard in the hole because they had committed the "perfect crime" but could get caught if the guard got out. Matt later told his friend Tom "everything" about stealing from Ms. Dillard. Bragging about what they did is certainly no way to help ensure they would not get caught.

Stupidity: When Jonathan is chasing the truck to try and save Sarah, he could have removed his heavy backpack and run faster...but instead just leaves it on. No wonder he wasn't fast enough.

Stupidity: Colette was holding the metal ladle close to the bottom of its long handle and near the top of the hot pot of stew she was serving, and yelled, "Ah." due to her hand getting too hot. She had a towel wrapped around the handle of the pot, but it was that hand that got too hot/burned (not the hand that was holding the metal ladle close to the top of the steaming hot pot of stew). (00:04:48)

Stupidity: When questioning the heavyset witness after his having seen Costner in the hallway, there is no mention of the most obvious identifiable feature...the pearly white Navy uniform he was wearing. Instead, Costner is described as being a common "everyman."

Stupidity: Rick tries to kill Frank at his boathouse by dumping gasoline all over the place and using Ray Coleman's lighter that Frank had. At this point, Rick has gasoline over his arm, but instead of properly cleaning it, he opens the lighter immediately and has his arm burned. Surely a criminal genius like Rick wouldn't have risked this as this is a loose end. Further mention goes to when he has the bathroom door open for no reason while medicating the burn mark, which enables his wife to see him and discover who he really is.

Stupidity: They have the technology to track the movement of the rebel troops, and while the Nigerian airspace is too hot for extract, the fighter jets landing behind Tom Skeritt on the carrier could easily wipe out 300 rebel soldiers.

Stupidity: Considering the movie takes place in the winter of '75, it seems unlikely that the babysitter would arrive in a halter top and barefeet.
Suggested correction: I agree that this is a "stupidity", but think your use of the words "it seems unlikely" allows for the suggested corrections already given. Perhaps replace "it seems unlikely" to "it isn't rational." Even if the daytime temperature was mild for winter, the temperature would probably drop by around 30° overnight.
Suggested correction: Actually, January of 1975 was very mild, much like the winter in the northeast this year, so it would not be impossible for the babysitter to wear unseasonable clothing.
Suggested correction: Ordinarily I would agree with this observation, however, I believe the girls outfit matches her carefree attitude. She did bong hits in the family bathroom, laid on the boys bed seductively and asked him if he French kissed so dressing comfortably to babysit isn't out of context.
Adding to this, almost every babysitter I had growing up went barefoot or at least shoeless. Even this past new years eve, the young lady who came to watch my kids took her shoes off as soon as she came in the house.
It is a common courtesy to remove shoes when entering someone's home to protect the carpeting (or other flooring) from getting soiled by whatever might be on the bottom of shoes after walking outdoors.
Maybe I'm wrong, but after watching this movie last night, it sounded like the girl was wearing flip-flops when she walked across the bathroom to open the door. Would it be rational for her to have worn sandals too?
Considering she was barefoot for most of the night, yes, she may have worn them for comfort.

Stupidity: After John's wife is taken he follows them. Four of them spend a good 5-10 minutes shooting the hood and down the side, he pulls right up next to them and they still shoot down the side. Why didn't they just shoot right inside the windows or or windshield? Should have been very easy since all the windows were down and John had knocked out the windshield. John would have been dead and their troubles over.

Stupidity: When the police officer goes to Mac's foreclosed house and asks Lucas (who just came out) for identification, Lucas does not start looking for his wallet/ID. Instead, Lucas tells the officer he thought the auction was that day and was interested in buying the property because he needs space for his horses to run. Before Lucas produces ID, the officer gets another call and has to leave. The officer leaves without even jotting down the license plate number of the SUV. (00:39:58)

Stupidity: One of the major reveals and plot twists of the movie lies in the fact that a certain character is an accomplice of the medium. The reveal, though, does not explain at all how said individual managed to fool Poirot; the trick briefly shown involves a simple rope pull to open a door. Poirot was looking exactly for that kind of trick, paces around the room constantly on maximum alert, and examines the door itself later. Likewise, it does not explain where and how they could hide the stuffed animal.