THE SOLUTION to a bad guy with a gun, it is often said, is a good guy with a gun. Yet according to Dallas Mayor Mike Rawlings (D), there were 20 to 30 good guys openly carrying guns among the protesters whom Dallas police were supervising last Thursday night, when Micah Xavier Johnson began picking off officers. “In the middle of a firefight,” the mayor said Sunday, “it’s hard to pick out the good guys and the bad guys.”

In fact, the presence of so many guns could have made Thursday’s massacre worse. Officers did not know where the shooting was coming from, how many people were involved or what kinds of weapons they were facing. Innocent protesters publicly toting guns became immediate suspects. Their presence fed the confusion and amped up the danger.

Yes, guns can be properly and effectively used in self-defense. But saturating the nation with firearms also primes the country for deadly violence, making many situations more likely to end in death.