Last Thursday yet another angry white man went on a deadly shooting rampage. This time, the target was a newspaper, the Capital Gazette in Annapolis, and the shooting left five dead and several others wounded. And like the scores of mass shooters who came before him, Jarrod Ramos had a long and well-documented history of misogyny and violence against women both online and in person. In fact, his story helps to confirm the ways in which online harassment often serves as a precursor to offline violence, and should therefore be taken more seriously.

Ramos’s history of online harassment was at the ...