I’ve always listened to the sort of music that you’re not really supposed to listen to, so the concept of the “guilty pleasure” is one I don’t particularly dwell on. There are lists of these all over the internet, but I would guess that the real reason people listen to ABBA and Journey is that they actually enjoy them, rather than for any sense of irony.
The only convincing use of the phrase I’ve seen was in Bill Bruford’s Autobiography, in which he says music itself is a guilty pleasure. He spent most of his life on tour, unable to see his family, and therefore felt genuinely bad about doing something that he enjoyed. Somehow, listening to Hanson doesn’t seem to be anything you should worry about.