The only problem is, in the movie, the government shut down all emergency services during the “Purge”.
In real life, the cops will still be out tonight.
The perps may be encouraged by the “stand back and watch/contain” attitude the cops had the first night of looting, saving the SWAT gear for (more or less) peaceful protesters. Start enough coordinated chaos, and the wantonly evil can make headway they only dream of individually.