Wanting to be notorious and also well-liked is an oddly forked ambition, but for 40 years now John Waters has been treading his double path. In books such as the new Role Models he gives the paradoxes of his image some fine-tuning. The essay on art collecting has some charmingly brisk advice for the beginner (go to the second show of an artist you like and buy something for about $5,000) and everything on his list of Five Books You Should Read to Lead a Happy Life if Something is Basically the Matter With You is worth knowing. But the real message is: "Bet you didn't think that a film-maker best known for a scene of shit-eating would respond so fully to the drawings of Cy Twombly and the prose of Denton Welch, huh?"

When it comes to interviewing the singer Johnny Mathis, his "polar opposite", the mismatch isn't perhaps as great as Waters thinks. It's hard to feel the contrast as electrifying in a world where Tony Bennett can play Glastonbury. In theory, Waters became interested after seeing Mathis off duty but effortlessly in role ("I never got over seeing Johnny Mathis in the parking lot"), but perhaps the epiphany has been surgically enhanced. Other things in the book that Waters never gets over include the media circus of the Manson trial and a show by minimalist sculptor Richard Tuttle.

Print interviews are routinely pieced together after the event, using snippets of transcribed dialogue to support a more or less fictitious narrative. Waters's interview with Mathis is extreme, though, in the way it keeps its supposed subject dangling. Waters follows Mathis's bland revelation that he has learned to "be the audience", so that the same old song list always feels new, with the sentence: "What perfect advice, agrees the other top role model from my deep dark past, Patty McCormack," transporting us to another time and place. This leads to eight pages of irrelevant material, not just scraps of an interview with McCormack (an actress mainly known for one childhood role) but a digression about Bobby ("Monster Mash") Pickett. The impression given by this perverse piece of construction is of Mathis waiting politely for his visitor to emerge from narcissistic reverie.

The obvious inadequacy in Waters's worldview is that he thinks things such as abuse, addiction and psychosis are essentially fun. The damaged performers who gave his early films vitality knew better. Waters's parents may have been conventional but they were supportive (his mother, for instance, delivering him by car to a louche bar when he was still under age). From this secure perspective, disorder looks liberating, and survival is never threatened. Anyone who can say that "all children of insane mothers" learn to view their upbringing "with a certain bemused detachment" deserves a slap, if only from me. If this was true then maladjustment would be self-correcting; social services departments could shut up shop tomorrow.

Interviewing the daughter of a Baltimore legend, he asks: "Could you ever see the comedy in your situation when Zorro was alive?" No, John, that would be you, from your exploitative distance. Considering that "Lady Zorro" was the stage name of a lesbian burlesque performer, "an angry stripper with a history of physical and sexual abuse with a great body and the face of a man," and that her daughter, drinking and smoking dope by the age of 11, was essentially the adult in the household, the reply of "Not at all!" seems moderate. Waters tries to persuade her that it wasn't so bad ("She raised a daughter who is reasonably happy and well-adjusted, and isn't that the best you can say about any mother?") while knowing nothing about it. He was lucky not to be thrown out of the house. For decades Waters has gone by the nickname "The Pope of Trash", but perhaps "Pervert Pollyanna" comes closer to his exasperating essence.

The longest piece in the book concerns a long-term prisoner ("Her name is Leslie van Houten and I think you would like her as much as I do") whose parole prospects have been unjustly denied over the years. For decades Van Houten has taken responsibility for her actions (she took an active part in the murder of two strangers), yet she has served more time than any Nazi war criminal not actually sentenced to death at Nuremberg, and more than the surviving female members of BaaderMeinhof.

I accept these arguments, while questioning Waters's right to make them. There were certainly extenuating circumstances, such as drug derangement, brainwashing, group hysteria  psychological factors that he suddenly starts to take seriously. It's just that I find myself wondering who is being rehabilitated in this piece of prisoner outreach.

The murders were of Rosemary and Leno LaBianca, committed by the Manson "family". It's not that I think those killings were in a special category, beyond atonement. It's true that in his advocacy of the repentant killer, Waters strikes a queasy tone that seems to slight innocent suffering: "Her participation in the LaBianca murders was a very real atrocity that she could never make go away like a bad hairdo or a dose of hippie clap. This was no youthful recklessness that today some baby boomer might turn into a nostalgic tattoo. No, this was fucking awful. I used to joke that 'we've all had bad nights'; well, Leslie really had a horrible one! But of course the LaBiancas' night was much, much worse."

My objection to him striking these creepy poses is that in 1971, after attending the trial of some minor Manson family members, he can describe himself as "heavily influenced" and "actually jealous of their notoriety". In fact he dedicated the next film he made, Pink Flamingos, to "Sadie, Katie and Les"  Manson disciples. Shouldn't Waters stick to just the one brand of shamelessness?