The appearance on CNN came the day of President Trump's controversial press conference, at which Trump reiterated remarks that blamed "both sides" for the recent violence in Charlottesville, Va. between white supremacists and counter-protesters.
After ending his show that night, the 63-year-old Oscar-winning filmmaker delivered, rounding up his audience in buses and, together, heading to Trump Tower where the president is now staying for the first time since his inauguration.
"We are here to perform a citizens arrest - well there's lots of police there, maybe they'll do it for us", Moore announced upon arrival. Americans have died because of that.
Ruffalo, who was in the audience, said that the group would "walk the next three blocks down to Trump Tower to get as close as we can so he can hear us... we want him to hear us".
"For the sake of the soul of our country, we must come together to restore our national dignity that has been robbed by Donald Trump's presence in the White House", Moore said in a statement.
Michael Moore, Mark Ruffalo Lead Trump Tower Protest After Broadway Play
Singer Demi Lovato posted a series of tweets saying her heart "continues to break the more I watch the news".
"There is no many sides to this, there are two sides: there's Nazis and there's people who fight Nazis", Ruffalo said.
"He's allowed these people, he's allowed fascism, he's allowed the KKK, he's allowed Nazis to show their ugly face, and we're here to remind him there's a cost for that."
White nationalists, neo-Nazis and other far-right extremists assembled last Saturday to protest a decision by the city of Charlottesville to remove a statue of Confederate Gen. Robert E. Lee. Say her name: "Heather Heyer!". "Stealing the show, though, was definitely Olivia Wilde, who eventually met up to march with Moore and Ruffalo, carrying a giant sign emblazoned with the hashtag "#RESIST", which makes flawless sense for an actress who starred in an adaptation of George Orwell's dystopian 1984. Texas has said it will attack the legislation in court unless Trump announces a phase-out program by September 5.
While reviews of Michael Moore's Broadway debut have not been kind, that hasn't stopped the liberal firebrand from stirring the pot when it comes to criticizing U.S. President Donald Trump, and he took things to a whole new level on Tuesday night - with the help of one of the Avengers.