Well, you made things interesting by asking about "music that I now hate, that I used to love". (With the "used to love" bit making it pretty impossible for me to think of any music that falls into that category. If I loved some music before, I still at least like it, or tolerate it in the very worst cases. And any music that I actually hate, I don't think I ever liked, but perhaps I tolerated it. (i.e. Tolerating meaning that I wouldn't turn it off if it came on the radio.)
However, if you had said music that I now dislike, that I used to like, I can think of a few examples, including:
Foreigner
Styx
Jackson Browne
(Basically any of those bland '70s and '80's bands)
PS So Tan43,
Since you mentioned that you now hate "Disco", (which given the question means that you used to "LOVE" it), I am afraid that as a member of the Audiophile Police, we are hereby revoking your membership in the Audiophile community.
Sorry, but you gave us no choice!
Please turn in your turntable at the door on your way out!
;-)