Lyric discussion by Gert1980 

Cover art for Slideshow lyrics by Rufus Wainwright

Back then Rufus was just in his relationship with Jorn Weisbrodt, so I think the song is about their then early relationship. But I've also heard stories about how his mom always used to make slidehows from all their familyvacations and that he paid her tickets to come visit him and Jorn in Germany and that this song was about that and him demanding to be in her next slideshows. But since Rufus never was one for serious relationships before he met Jorn, to me this song is about him dealing with a serious relationship!

My Opinion

"You treat me so indifferently" does not sound to me as if the song is addressed to Kate. Supposing the slideshow rumour is true, that may be where he got the slideshow idea and transferred it to another sort of relationship.