Despite uniting nearly 5,000 signatories against the Paramount–Warner Bros. merger, Mark Ruffalo is fighting just as hard for those in Hollywood who wouldn’t sign the recent open letter.

The 4x Oscar nominee recently noted that there is “a deep, ugly and pervasive fear of speaking out” in the entertainment industry right now, as many “were afraid” to sign his letter urging state officials to block the hostile takeover.

“This plan is already in motion,” he and American Economic Liberties Project director Matt Stoller wrote in a New York Times op-ed. “Within weeks of Paramount winning the bidding war for Warner Bros., we helped bring together a loose coalition of civil society groups, unions and actors, and this coalition enlisted over 1,000 artists to sign an open letter indicating our support of state attorneys general efforts to block the takeover. Many more subsequently added their voices, and the letter now has nearly 5,000 signatories.”

They continued, “But the most revealing thing about that letter wasn’t the people who signed. It was the people who didn’t. Not because they disagreed — because they were afraid. There are many reasons to block this deal, but we now believe the most fundamental one is what we encountered when asking artists to use their voices: fear. A deep, ugly and pervasive fear of speaking out.”

“We heard time and time again from artists, when asked to sign this letter, that they supported it but were afraid of retribution. Their fear is not unjustified,” the pair added, noting several examples of alleged retaliation, including WB’s CNN pulling a segment discussing the merger, on which Ruffalo was supposed to appear.

“This merger will cause many harms in Hollywood,” they wrote. “But one is already in effect: People are afraid to say what they think about their own industry.”

In February, Netflix threw in the towel on the Warner Bros. deal, refusing to raise its bid against Paramount Skydance’s “superior” $31-per-share offer, following the $82.7 billion deal Netflix signed with WBD in December before the Ellison-owned company launched its hostile takeover.

Last month, Ruffalo and Stoller were among more than 1,000 signatories on the letter claiming the merger will “threaten the sustainability of the entire creative community.” The letter, which has since grown to nearly 5,000 signatures, was organized by the Committee for the First Amendment, the Future Film Coalition, the Writers Guild of America and the Democracy Defenders Fund.