An advertisement for the National Rifle Association that features a spokeswoman calling on the group’s supporters to strike back against protests by the left “with the clenched fist of truth” has become one of the latest flash points for partisan anger.

In the video, Dana Loesch, an N.R.A. spokeswoman and popular gun-rights pundit, identifies a set of foes — the media, schools, Hollywood elites and President Obama — that she says are inciting demonstrators to violent protest against President Trump.

“All to make them march, make them protest, make them scream racism and sexism and xenophobia and homophobia,” she says, as black-and-white images of recent protests play in the background.

“To smash windows, burn cars, shut down interstates and airports, bully and terrorize the law-abiding until the only option left is for the police to do their jobs and stop the madness.”