For full context (and the interview with Jodorowsky is from 1970 also):

In regard to the filming of the rape scene, Jodorowsky said

When I wanted to do the rape scene, I explained to [Mara Lorenzio] that I was going to hit her and rape her. There was no emotional relationship between us, because I had put a clause in all the women's contracts stating that they would not make love with the director. We had never talked to each other. I knew nothing about her. We went to the desert with two other people: the photographer and a technician. No one else. I said, 'I'm not going to rehearse. There will be only one take because it will be impossible to repeat. Roll the cameras only when I signal you to.' Then I told her, 'Pain does not hurt. Hit me.' And she hit me. I said, 'Harder.' And she started to hit me very hard, hard enough to break a rib... I ached for a week. After she had hit me long enough and hard enough to tire her, I said, 'Now it's my turn. Roll the cameras.' And I really... I really... I really raped her. And she screamed."[1]

He went on to state, "Then she told me that she had been raped before. You see, for me the character is frigid until El Topo rapes her. And she has an orgasm. That's why I show a stone phallus in that scene . . . which spouts water. She has an orgasm. She accepts the male sex. And that's what happened to Mara in reality. She really had that problem. Fantastic scene. A very, very strong scene."