Shannon Watts knew she was heading into a rough neighborhood when she became an activist in the battle over gun control. A former corporate executive and mother of five children, Watts launched a gun-control group, now called Moms Demand Action for Gun Sense in America, not long after the Newtown shootings. As the new push to restrict guns grabbed attention over the ensuing year, Watts and other activists experienced the blowback up close, in sometimes frightening detail.

At protest rallies, they have been met by men carrying rifles. (It's legal: many states permit the open carry of “long guns.”) Watts has had her home address in Indianapolis posted online along with the suggestion that “people show up and show why it’s important to have a gun.” She has gotten letters at home saying that the sender knows where her kids go to school and where her husband works. On the lighter side, an ironist has been sending her free issues of Guns & Ammo.

She has a harder time finding irony in images floating around online featuring her head bloodied by a huge knife stuck into her skull.

As the anniversary of the Sandy Hook Elementary massacre nears, the gun politics battle is playing out not only in Washington and state capitals, but on the Internet, where some gun-rights defenders have decided to counter the social-media strength of gun-control supporters (Moms Demand Action now has more than 127,000 followers on Facebook) by resorting to aggressive online harassment. The targets of the harassment are taking it mostly in stride, viewing it as a sign that they’re having more impact than downbeat media assessments of the gun control movement typically assume.

“The more traction we get, the more it becomes very, very aggressive,” Watts said in an interview. “Their concern level is so heightened that they’re going to fight back with everything they have.”