Denis Henigan, the vice president of the Brady Center to Prevent Gun Violence, based in Washington, D.C., said there is cause for concern. He said small "extremist" gun groups are sprouting up across the country, creating problems for gun-control efforts and the NRA.
"I think these groups are actually willing to act out the NRA's vision for America," Henigan told "Nightline." "When you have people who are openly carrying their guns into Starbucks, it causes enormous concern among other people who are going into Starbucks. It causes backlash."
Starbucks was the target of a pressure campaign to allow customers to openly carry their weapons in states where it's legal to do so -- that's 43 of the 50 states.
It was not a campaign organized by the NRA.
Pro-gun grassroots groups used social networks, bulletin boards, Internet chat rooms and text messages to get the word out -- a testament to their influence, even without the backing of the umbrella organization. Van Cleave called the grassroots efforts "critical."
"More guns in more public places is what protects people," he said.