Stupidity: The mercs are said to drop in, in broad daylight. Approx four men are furthermore able to drop with plenty of ammo and at least one high calibre rifle, but they do not bring mines to secure roads nor drones to map the area.
Stupidity: The patient was wearing a white and gray striped tie when he was walked into the ambulance. The EMT did not remove or even loosen the patient's tie (to facilitate breathing). Instead, the tie was moved from the front to along his shoulder/neck, apparently to get it out of the way while she was cutting off the patient's shirt. (00:07:50 - 00:08:20)
Stupidity: The ending has a bit of a twist; apparently, octogenarian college professor Morgan Freeman somehow chased down and murdered offscreen 6'3" professional assassin Vernon Davis. That's not the toughest part to swallow, though; he also sent the two detectives (one of whom he is not even supposed to know of) via UPS 2-day delivery mail some body parts of his victim. We don't know which part Lavazzi gets (genitalia were mentioned earlier), but Boyd gets the eyes and decides to eat them. For starters, unrefrigerated 2-3 day old eyes would never look as pristine as the ones Boyd gets. Also, Morgan Freeman mentioned earlier in the movie that for the power of Muti to be effective, the body parts need to be taken from a victim that is alive, screaming, and eaten only mixed with herbs and other catalysts. So what the detective does doesn't make sense even in the movie lore.
Stupidity: Makes for a funny one-time gag for the benefit of the audience, but it doesn't really make sense that Jay would walk into the hitman's place without knowing he was deaf. It's not exactly the kind of detail that Tommy T. would not mention. In fact, it's the only thing he told the police, apparently, since they, on the other hand, show up knowing he's deaf but do not know he's a big ginger dude and are therefore initially fooled by his squatter story.