From an article entitled "On the Banks of Lake Lemon.  Mr Nabokov Reflects on 'Lolita' and Onegin,"  by Douglas M. Davis In The National Observer (29 June 1964), p. 17:

"The author believes too many critics overlooked the change that takes place in Humbert Humbert, the book's 'hero,' during the course of his affair with Lolita [sic]. 'I don't think Lolita is a religious book,' he says, 'but I do think it is a moral one.  And I do think that Humbert Humbert in his last stage is  a moral man because he realizes that he loves Lolita [sic] like any woman should be loved.  But it is too late; he has destroyed her childhood. There is certainly this kind of morality in it."