For 55 months, protesters have demonstrated outside the National Rifle Association headquarters in Fairfax, Virginia. In snow, rain and blazing sun, they have met to mark each month since 14 December 2012, when 20 children and six adults were shot dead at Sandy Hook elementary school in Newtown, Connecticut, and to protest NRA influence over the lack of action by Congress on stricter gun control laws.

On Friday, between 400 and 500 people lined both sides of the street outside the gleaming, modern NRA building. Usually, the 14th of each month brings a dedicated crowd of 30.

About 20 armed counter-demonstrators from a local group marched along the street, carrying signs that supported gun rights and touted the benefits of good guys with guns.

“Shame! Shame!” the gun control protesters cried.

Friday’s protest, organized by the Women’s March on Washington, honored the protesters who were there every month and sought to expand their agenda, with a focus on what protesters called the coded NRA attacks on black and brown Americans and a failure to defend Philando Castile, a licensed gun owner shot dead by a police officer during a traffic stop in St Paul, Minnesota. The officer was cleared of all charges.

The protest came in the wake of an incendiary recruitment ad for the gun rights group, in which an NRA spokeswoman raised fears about violent protesters and said the NRA had to confront such groups with the “clenched first of truth”.

With an ally in the White House and Republicans controlling both houses of Congress, the NRA faces no threat of new federal gun control laws. The problem facing the NRA, one analyst said after the 2016 election, was what to do when it had won so much.

The NRA’s answer has been to portray its members as the “counter-resistance”, and to portray the resistance against Donald Trump as an existential threat to American freedom.

In a speech in February, Wayne LaPierre, NRA executive vice-president and CEO, criticized federal judges for ruling against the president in the cases sparked by Trump’s travel ban.

National Rifle Association supporters stand among gun control advocates as they rally outside the NRA headquarters in Fairfax, Virginia. Photograph: Jim Lo Scalzo/EPA

“Leftwing judicial activism” is a “form of violence against our constitutional system”, LaPierre said, comparing judicial rulings to throwing “a molotov cocktail at the US constitution”.

A month after January’s Women’s March on Washington drew millions of peaceful protesters, many wearing hand-knit pink hats, LaPierre assailed the liberal resistance, saying protesters “all share one thing in common: they’re angry, they’re militant, and they’re willing to engage in criminal violence to get what they want”.

After the NRA released its controversial “clenched fist of truth” ad, the Women’s March co-president Tamika Mallory demanded that the NRA apologize. She then organized a demonstration that would take protesters from NRA headquarters to the the justice department in Washington.

The NRA’s only comment prior to the protest was another video featuring spokeswoman Dana Loesch, released on Thursday, which attacked the organizers of the Women’s March as “anarchist angels”.

On Friday morning in Virginia, as protesters waved signs and set up a mural showing Sandy Hook victims, the only visible NRA presence was a handful of discreetly dressed men with earpieces, standing inside the gates. The group’s public firearms museum, one man said later, was closed.

After speeches from a range of advocates, including a survivor of the Pulse nightclub shooting in Orlando last year, and a statement from Philando Castile’s mother saying the NRA should be ashamed for not supporting her son, marchers set off early. About three miles into the 17-mile march, in 90F (32C) heat, they paused for lunch, water and stretching at a Subway sandwich shop.

Supremia Bostika, who had driven more than two hours from Newport News, Virginia, to attend, said she had watched the NRA ad and found it “kind of offensive”. Bostika, wearing a Black Lives Matter T-shirt, said the ad was “flipping the script” and trying to portray protesters as violent and threatening, which was not the case.

Her comments were interrupted by a request from an organizer for the group to form a circle and do some group stretches to prepare for another three miles of walking.

“Yoga!” one protester exclaimed, brightly.

Afterwards, more than 130 protesters continued to march two-by-two along a busy road, the sun blazing overhead. They had about 15 miles to go.