Mark Cuban has finally had enough of the very ideology he once enabled. The liberal billionaire and media-savvy entrepreneur torched the far-left social media bubble on Bluesky this week, calling it “hateful” and plagued by “groupthink” that stifles real debate and punishes dissent.

Once pitched as a safe space for liberals fleeing X—formerly Twitter—Bluesky has exploded in popularity since President Donald Trump’s return to the White House in 2024. But that same mass migration of leftists has turned the platform into exactly what Cuban now criticizes: an ideological echo chamber, boiling over with anger and intolerance.

Cuban posted bluntly on Monday, “The replies on here may not be as racist as Twitter, but they damn sure are hateful.” He went on to say that any attempt to talk about topics like AI or healthcare is met with vitriol or silence. “Talk AI: FU, AI sucks go away. Talk Business: Go away. Talk Healthcare: Crickets.”

It wasn’t always this way, at least not in Cuban’s mind. After Trump’s landslide victory in 2024, Cuban joined Bluesky and wrote, “Hello Less Hateful World.” But less than a year later, his optimism has curdled into disappointment.

“Engagement went from great convos on many topics, to agree with me or you are a nazi fascist,” Cuban wrote, highlighting the platform’s descent into ideological purity tests. “We are forcing posts to X,” he added, implying that real discussion had to go back to the very place liberals abandoned—Elon Musk’s more open, often combative X platform.

Bluesky, created by Twitter co-founder Jack Dorsey, saw its user base triple from 10 million to 30 million between November 2024 and May 2025. It became a magnet for progressives like Mark Hamill, John Cusack, and Stephen King, who preferred its left-leaning culture to the uncensored debate on Musk’s X. Dorsey himself resigned from the Bluesky board last year.

But Cuban now says the very thing that attracted the left to Bluesky—its ideological purity—is suffocating the space. He even shared a Washington Post op-ed titled “The Bluesky bubble hurts liberals and their causes,” which argued that users only get engagement if they toe the progressive line.

Cuban’s reaction: “The lack of diversity of thought here is really hurting usage.”

The column’s premise is simple: platforms like Bluesky become counterproductive when they drive out anyone who doesn’t parrot the latest progressive orthodoxy. And Cuban’s personal experience confirms it.

This comes at a moment when the American left is already grappling with internal fractures and a growing backlash over their intolerance of opposing views. Cuban’s frustration echoes a broader awakening among liberals who once championed “open dialogue” but now find themselves silenced by their own side when they stray from the script.

While Cuban has never been a conservative darling, his recent comments are striking in that they validate what many on the right have been warning about for years: the authoritarian instincts of the modern left are not just attacking conservatives—they’re devouring their own.

Whether Cuban will return fully to X—or even support Trump’s broader free speech agenda—remains to be seen. But what’s clear is this: when even a liberal billionaire can’t speak freely in a liberal space, the left’s “utopia” is starting to look a lot more like a digital dictatorship.