Duterte, who promises mass killings of suspected criminals if elected next month, has faced a storm of criticism since a video showed him making crude remarks about a female Australian missionary who was raped and killed during a Philippine prison riot in 1989.
The video uploaded on YouTube shows Duterte, who was mayor of the southern city of Davao where the riot broke out, telling a crowd of laughing supporters: "I was mad she was raped but she was so beautiful. I thought, the mayor should have been first."
Villegas posted the video on social media, telling the faithful: "Please watch the video and judge for yourself. I will keep my own judgement to myself."
In response to Villegas, Duterte - who is still mayor of Davao - issued a statement today saying: "All the while I was doing my duties for humanity. And now they're castigating me for my mouth?"
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Asked if the bishop might be warning people not to vote for him, a defiant Duterte said: "Correct."
"If it is not acceptable to the cultured people, let it be. If it means my defeat, so be it," he said.
Australian ambassador Amanda Gorely joined the critics, saying in a statement on Twitter: "Rape and murder should never be joked about or trivialised. Violence against women and girls is unacceptable anytime, anywhere."
Duterte, who leads in the latest opinion survey of presidential candidates in the May 9 elections, has refused to apologise for his remarks, saying he was merely relating a "narrative" of events during the 1989 riot and not making a joke.