I'm going to tell you a secret. I'm going to explain something that no one else understands and, hopefully, you'll learn something from this.
The reason he loves Elvis Costello is because hearing songs about the cruelty women (as well as other people) are capable of makes him feel justified in cheating, lying, stealing, "experimenting," and being a manipulative, all-purpose fuck.
The reason I love Elvis Costello is because he comes from a place of vulnerability. He isn't afraid to show the pain brimming just below his black-rimmed glasses. He has no problem with people hearing his tales of bitterness and self-loathing and doesn't do it for catharsis or for pity or for him to be able to say "Dangit, I'm a nice guy," but because he simply must.
But him? He's got no idea that he's the one being sung about in "I Want You." He's the one that "tossed some tatty compliment your way."
I hope I was able to clear that up. As you were.