Stupidity: When Chili, the hippy stoner chick, goes upstairs and sees Jason holding a fire poker, she runs back downstairs and heads to the door. Then the door gets blown open by the wind...and then she runs back inside for no particular reason and gets killed by Jason.
Stupidity: Milton, straddling Edie's body on the floor, is about to pull the plastic sheeting over her head. Edie's eyes suddenly open, and she starts screaming. Instead of quickly pulling the plastic sheeting over her head and suffocating her, Milton half-heartedly struggles to control Edie's hands, which she somehow manages to raise from alongside her body and around his to be in front of her neck. (00:38:50)
Stupidity: On the phone, Marion told Paul, "I'm nearly certain she'll [Maggie] get full custody, but if you fight this, you stand to lose everything, even visitation to see your daughter. Sign the contract..." Jeff wanted to see Jenny and, other than being unemployed for three years, there were no reasons his parental rights should be terminated. It was not "in the best interests" of Jenny to relocate to Seattle and never see her father again. Fighting it, Jeff would have likely won custody of Jenny. (00:15:39)
Stupidity: When Joey is trying to escape from the Cenobites, she bumps into a man who calls her "Baby" and wonders where she's off to in such a hurry, possibly because he's looking for a booty call. The streets are literally on fire (there's a huge flame right next to the man) and buildings are exploding. Even if he's extremely horny, he should still be able to tell a woman doesn't want to stay around with so much chaos and destruction happening around them.
Suggested correction: The dude was probably high on various types of drugs and probably didn't even know where he was. Just a thought.
Too high to recognize buildings exploding and fires bursting from out of nowhere, but not too high to recognize a woman in distress?
He didn't recognize much did he? Well, he saw she was female. But not really what was going on.
He recognized she was off somewhere in a hurry. He also had a pretty instant reaction to seeing the Camerahead Cenobite.
Stupidity: Why would they drive all the way to Marylebone Railway Station in central London when Southbury Road station is only a thirty-second drive away?
Stupidity: Two oil rig workers were looking at two young ladies in bikinis who were sunning themselves on a boat/yacht. One oil rig worker said, "That's where we should be right now. With them, enjoying the sun, instead of baking in it." Both men had double layers on - a jacket or sweater over a jersey or T-shirt - and one man was wearing a tossel cap. Even if it gets cold on the rigs at night, they did not need to be dressed in warm attire during the sunny daylight hours. (00:10:35)
Stupidity: When one of Vincent Price's protege's leaves a wax work-in-progress, he doesn't cover it with a lightly damp cloth, which is very important: wax uncovered will go hard and useless.
Stupidity: Harrigan leaves his partner's badge on his grave where anyone could take it and use it to impersonate a cop or abuse it in other ways. (00:50:15)
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: The marble somehow got under Don's skin at the bottom of his leg and was moving up the length of his body. Instead of heading off the marble in order to intercept and stop it from continuing up his leg, Don got a knife/box cutter and jabbed it into his skin near the bottom of his leg and trailed the marble, causing a long gash that served no purpose (other than creating a lot of blood and making a gory scene). The marble eventually exited his body via his eye. (01:04:40)
Stupidity: Charlie set her mom's blouse sleeves on fire and mom/Vicky just stood in the same spot, holding her arms (burning sleeves) out in front of her until Andy came and smothered the flames with a blanket. Even children know to "drop and roll" or put fire out by smothering it. (00:22:56)
Stupidity: Near the end, Sydney Wells and Paul Faulkner try to rescue a little 10-year-old girl who is trapped in the recreational vehicle. Sydney is banging on the door from the outside while the little girl is banging on the door from the inside. Paul then smashes out the door window, reaches inside and easily releases the door latch in one move. So, a 10-year-old girl was "trapped" because she couldn't simply open a door latch? Stupid.
Stupidity: How would a devout catholic like Angela not believe in the devil, as she tells Constantine? Makes no sense.
Suggested correction: Some Christians don't believe in the literal personification of the Devil. They see him more as a metaphor for all human sins. So according to them, the Devil is not something to blame evil on. Everybody has God and the Devil in them.
Stupidity: Possessed child Nicholas made the cross from a necklace pierce Fr Louis in the neck, causing blood to gush out. Fr Peter yelled, "Fr Louis, Fr Louis" as Fr Louis tried to pull out the cross. No one else present rushed over to try to help stop the bleeding or assist him. Fr Louis' sash could have been used around his neck to apply direct pressure to the wound. (Although it might have been obvious that it was a fatal wound to the neck, someone should have at least tried to help). (00:07:15)
Stupidity: After Danny kills Kat on the sidewalk, he just stands there with Rory while the other gang members flee to their vehicles. William comes running out of the Mexican restaurant and Rory tells Danny, "We gotta go, brother. Now." Rory sees William and gets into the vehicle without getting Danny to go with him. The gang drives away with Rory watching out the window as William tackles and fights with Danny. Rory and the rest of the violent gang left behind someone who just passed the initiation. (00:07:10 - 00:07:40)