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: Do the military routinely show up at a civilian's house and then pump thousands of rounds into the house without even verifying if anyone is inside? I've heard of suspension of disbelief, but this scene requires driving it to a vacant lot and abandoning it. (01:11:30)
Stupidity: When he's using carbon monoxide to poison the corrupt detective Frank Masters, the windows in the car were operated by the key fob. Unusual, but OK. Maybe. But the detective could've simply opened the doors after McCaul left him in there. The door worked when he was forced into the car. (01:24:30)
Stupidity: Four H.S. seniors are sitting in an SUV. A storm quickly intensifies and Billy gets out of the back seat to get a better look (wipers are on "fast"). Seconds later, Billy spots a tornado coming. Marcia (driver) tells Billy to "get in." Needing to flee the fast-approaching tornado, Marcia wants to leave as soon as Billy is in the SUV, so she yells, "Billy, get in!" The tornado is feet away when Billy closes the door - whew, he's safe! Marcia STARTS the SUV when the tornado starts bashing it. (00:01:14 - 00:01:38)
Stupidity: If Leo wants to kill his son's killer at any cost and no matter what happens, he should've gone directly to his House when the purge starts.
Suggested correction: He absolutely is headed there, but we see at least one incident where his path is blocked due to people out purging, and he needs to turn around. That detour caused him to go a different route, which led him to the mother and daughter. We even see him struggling with the decision on whether or not to help them. He decides to do so, and the rest of the movie unfolds as we see, but there is no mistake.