MANILA, Philippines — President Rodrigo Duterte on Wednesday disputed claims that shabu or methamphetamine does not damage the brain, saying users of the “virulent drug” have committed violent acts.

United Nations (UN) Special Rapporteur Agnes Callamard, a critic of Duterte’s war on drugs, recently tweeted a statement by African-American professor Carl Hart, who claimed that there is no evidence that shabu leads to violence or causes brain damage.

Hart, the chairman of Columbia University’s Psychology department, made the statement during a forum on illegal drugs at the University of the Philippines last week.

In a talk last week, he said that the "myth" that shabu shrinks the brain is from animal tests where animals that were given "large doses" of methamphetamine—higher than users normally take—had damage to their brain cells. He said, however, that the test animals developed a tolerance for the drug. Hart, who co-wrote a text book called "Drugs, Society, and Human Behavior," said that animals that were later exposed to larger doses over several days did not exhibit the "toxic effect."

His statement went against Duterte’s claim that the constant use of shabu shrinks the brain.

'She should go on honeymoon'

Asked to react to the claim, Duterte said Callamard and Hart should go on a “honeymoon.”

“She should go (on) a honeymoon with that black guy, the American. I will pay for their travel,” the president told reporters at the Ninoy Aquino International Airport Terminal 2.

“They should be together and discuss (these things)… If shabu were good, (if it) is really in consonance with their pronouncement, you can be sure that beginning tomorrow, I will provide shabu in the streets. You may get your fix if you want,” he added.

Neither Callamard nor Hart claimed that shabu is good or that illegal drugs are not a problem.

Duterte called Hart a “fool” who peddles “b***s***.” He said his statement about shabu was based on an American forensic study.

“That's all b****s*** to me. That is why I will not talk to them because my experience until now and 23 years ago when I became the mayor of Davao City was always a lot of violence and killing because of shabu,” the president said.

“He (Hart) said shabu does not damage the brain. Kaya pala pumunta dito ‘yung p***** i**** ‘yon, sira na ang ulo at mag-a-announce dito (That’s why that son of a b**** who has gone crazy came here to make announcements),” he added.

Hart did not say that shabu does not damage the brain.

Duterte said those who claim that shabu does not damage the brain have “prejudged” it as a harmless chemical

“Why would you sue me before the ICC (International Criminal Court) if you yourselves, son of a b****, claim that shabu does not harm people?” he said.

Nobody has said that shabu does not harm people but critics of the drug war suggest treating drug dependence and abuse as a health problem, an approach advocated by the Philippine Dangerous Drugs Board and that the government claims to also be doing alongside law enforcement operations.

“You have prejudged everything and you are referring to the core of the complaint against me. Why would I go there and hang myself?”

Last month, the lawyer of self-confessed hitman Edgar Matobato has asked the ICC to hold Duterte and other Philippine officials accountable for “crimes against humanity” that stemmed from the government’s war on drugs.

In a 77-page complaint, Jude Sabio said there are death squads running after suspected drug offenders and that law enforcers are aware of their activities.