Which doesn't make much sense since the violent and destructive actions they take have nothing to do with the source - the people they are hurting are just as innocent as the person who was hurt by the police (in this case). It's like saying my dog was run over by a car, so that justifies me breaking into your house and trashing it and stealing your stuff and getting away with it.
It's not supposed to make sense. It involves the instincts. As Nietzsche would put it, "Dionysian" (primal energies of the lower consciousness), as Freud would put it, the "Id." Same impulses engaged to the effect of enjoyment and excitement in action films like
Conan the Barbarian or
Predator. In a similar way, horror films tap into our fear to create "thrill."
Underlying assumptions about the nature of reality "envelop" our thoughts and perceptions like a heavy fog. For example, McDonalds as an endless source of cheap hamburgers and chicken sandwiches. In reality, every McDonalds has a limited supply of those food sources. Or, Long John Silvers will always supply the plastic utensils to eat their food with (one day I ordered a meal there and they said they were out of utensils. Employees shrugged at the people who asked how they were supposed to eat their meals without any utensils of any kind).
Similarly, stores are places where you get the items you want, line up behind the counter, and turn over money in exchange for leaving with the item. The "cloud of assumptions" that envelops our thoughts tell us that. But when you take away that "cloud of assumptions", then a store is just a place full of items. From a certain point of view, you don't "have to" put money on the counter or line up anywhere. You can just grab what you want and leave.
When riots break out, the anger within each person rises to the surface to clear away the "cloud of assumptions" that govern our usual behavior, allowing the primal energies of the lower consciousness to take over and displace our ordinary habits and beliefs with violence.
Same reason why atrocities break out during war, like those happening in Iraq right now. The "cloud of assumptions" that makes it difficult to imagine systematically beheading children clears away and is replaced with unrestrained fury that acknowledges no limitations to achieving its goal.
Generally speaking, looters are people who have (at least temporarily) lost belief in the power of the civil superstructure that allows for an orderly safe and existence. The "civilization instincts" that allow them to be a contributing member of society are going haywire.