The one unforgivable stupid plot hole that taints the entire movie.
When Ethan Hawke and family lock down for the purge... it's all good... then the black dude comes wandering down the street and Ethan Hawke's kid goes and opens the door for him to come in the house. So stupid.
Apparently, the special lock-down units don't have a child-protective cover on the switch TO OPEN THE DOOR! Give me a break. You pay millions of dollars for a top of the line security unit and you just push a button on the main panel to override your entire system??
Not to mention the kid no doubt knows how dangerous that night is... so what? Was he planning on rescuing everyone? I couldn't even pay attention after that because the entire family deserved to die after that point for raising one stupid idiot for a kid.