It's not so much he changed his views on pleasure, but that he was in love with her, and refused to contribute to her pain. He understood that she felt she would be using him, and that she would be unable to accept sex or anything from him as the gift it was. So he was all 'Hmph, no, it'll hurt you, and then you'll be mad and feel guilty. So, I would, but for that'
He also doesn't use the defense mechs with her at all - he knowingly reveals himself to her, because he does it to distract her from her pain. Pretty much everything he does, is for her. It'll make more sense, and be developed more fully the farther story goes along.
(Actually the ongoing problem that Zev has in the series is that he's never bothered to hide himself from her, but she refuses to 'see' that in it's entirity)