Breivik’s growing popularity and impact among right-wing extremists is partly a symptom of neglect. After years of debate, leaders are finally focusing on countering terrorist propaganda, employing thousands and spending millions on this important work. But terrorist manifestos, a rarified form of propaganda, are still being spread by prominent institutions of the very society that their authors seek to topple.

Read: Trump’s selective responses to terror

Hasson is only the latest acolyte that Breivik has attracted in the years since his 2011 attack. Both terrorists and nonideological killers have attempted to emulate him directly, with deadly results. The Newtown shooter Adam Lanza reportedly collected news clippings on Breivik’s attack and other incidents of mass violence before he killed 20 children at the Sandy Hook Elementary School. Other young men, such as the British college student Liam Lyburd, have been inspired to plan or carry out mass shootings based on their admiration for Breivik’s lethality, rather than his beliefs.

But for many others, Breivik has become an icon not simply of efficient violence but of ideological hate—for Muslims, immigrants, and their allies.

Even among extremists, Breivik’s status is contested. In online dialogues that I track as part of my work studying extremism, white nationalists and other extremists often argue bitterly over the value of his example. He has many detractors, some sincere, others contrived. Mealymouthed condemnations come from extremist ideologues who fear potential consequences when someone acts out the murderous fantasies they peddle. Strategic objectors paint such attacks as counterproductive, alienating to potential ideological sympathizers. Some complain about targeting—the fact that Breivik killed young Norwegians associated with the country’s ruling party, whose policies he rejected, rather than directing his rage at the Muslim immigrants he loathed and feared.

“I don’t agree with what Breivik did, but I could understand, my objection is what a waste thing to kill those young Nordics,” wrote one commenter on the neo-Nazi blog Daily Stormer in 2015.

On Stormfront, a white-nationalist message board where Breivik initially posted his manifesto, substantive threads about the rightness or wrongness of Breivik’s actions are frequently (but inconsistently) deleted by moderators, likely due to the platform’s stated policy of discouraging posts that explicitly encourage violence or illegal action. One neo-Nazi posting a critique of Stormfront on the site itself wrote, “Breivik did nothing wrong (apart from posting on this website).”

On the far less circumspect VNN Forum, Breivik’s acts have been robustly debated virtually since the day of the attack.

“If some enterprising American fellow, went to a youth camp in the Catskills, Camp David, or Martha's Vineyard, and ‘sprayed’ some young’uns belonging to our immigrant-loving [Jewish-occupied government], I dare say I might not lose a whole lot of sleep on account of it,” one VNN poster wrote just days after the attack. Others responding to the post at the time argued that the attack would only mobilize people against the movement, and suggested that Breivik’s acts were part of a Jewish conspiracy.