If you read May Pang's book, you'll see her perspective that she and John sometimes tolerated Mintz, and used him as a chauffeur. However, when John presented May with the birthday present of a used car, they exulted "No more Elliot Mintz!"
One of the reasons I don't trust Mintz is that he can't keep his story straight. I saw a recent documentary in which Mintz claimed that he and Lennon spoke on the phone every single day during the "Lost Weekend" -- and each time, the only topic John wanted to discuss was his obsession with returning to Yoko. Mintz has forgotten his earlier story (told to Jonathan Weiner) that Lennon would call him up begging to be taken to strip clubs and porno theaters. (In my opinion, the purpose of the earlier story was to deny the existence of John's intimate relationship with May.)
Mintz has been up to another devious activity recently, that of badly Photoshopping his image on to celebrity photographs. See the article "Elliot Mintz Photo Questions" on
meetthebeatlesforreal.com. There are a couple of examples on that page -- and others have uncovered many more examples of this.
Mintz has served as a spokesman for plenty of celebrities, so WTF would he do this? He wants to be perceived by the public not as a lackey for Yoko, but as a confidante of Lennon (among many others).
Mintz is obsessed with celebrities, and celebrities have used him to communicate dubious things to the public. I'm not sure that anyone finds him believable. There's a discussion between Mintz and Sean available online. For the occasion, Mintz over-decorated his suite with candles and flowers. Yet, even Sean shows some contempt for Mintz, making fun of some of his gestures and scolding him for a false promise he had made.