As Barcelona, Spain reeled from an attack on Thursday that left 13 people dead and dozens more injured, President Donald Trump quickly took to Twitter to both denounce the attack and recount a "vile" myth that claims a U.S. general—though the story has been thoroughly debunked—executed 49 Muslims with bullets drenched in pig's blood.

Study what General Pershing of the United States did to terrorists when caught. There was no more Radical Islamic Terror for 35 years! — Donald J. Trump (@realDonaldTrump) August 17, 2017

The fact that the story isn't true never stopped Trump from parading it around on the campaign trail.

"Trump is celebrating torture and mass executions here. This isn't law and order—it's war crimes."

—Adam BestBut the significant point is not that the story is apocryphal, many pointed out—it is that the story is "bigoted" and "vicious nonsense."

"Yes, it's false," wrote MSNBC justice and security analyst Matthew Miller. "But [it's] more important that [the president of the United States] is talking about executing Muslims without trial with bullets coated in pigs blood. Appalling."

Though Trump insisted that he needed "the facts" before speaking about the white supremacist violence in Charlottesville, Virginia last weekend, this concern was quickly dropped by the president in the case of Spain, where the attackers may have been motivated by Islamic extremism.

"Trump is celebrating torture and mass executions here. This isn't law and order—it's war crimes," wrote filmmaker Adam Best. "The Donald is clinging to the phrase 'radical Islamic terror' to avoid talking about white supremacist terrorism. So transparent."

Others reacted similarly:

Trump on Tues.: "Before I make a statement, I need the facts." Trump on Thurs. cites 'pants on fire' unproven claim https://t.co/U2LCcdDmtc https://t.co/Nc3Z3jt9Cr — Kyle Griffin (@kylegriffin1) August 17, 2017

He goes so far as to glorify war crimes against Muslims but calls domestic KKK terrorists "very nice people" who had a permit. — Eugene Gu, MD (@eugenegu) August 17, 2017

Trump condemns attack in #Barcelona in hours. Took days to condemn #Charlottesville attack when he said needed time to get "all the facts." pic.twitter.com/dW3P47HRnP — ChristianChristensen (@ChrChristensen) August 17, 2017