I could go either way on this one...but regardless music is music whether it suits your ears individually or not. Just remember that the same people who cling to the "rap sucks and it's not music" probably got it from their parents talking about "that rock and roll stuff is just noise and loud guitars". IMO you can't be a true musician until you can respect all of its outlets and use them to your advantage in your music.
I've listened to Nickelback and other bands/singers like them and some I like, some I don't. When you lived most of your life in a musically diverse household you tend to look at music a lot differently. My dad listens to bands like AC/DC, Aerosmith, Pearl Jam, Nirvana, Queen, Hendrix, Clapton, list goes on. Mom chose the typical top 40 stuff you would hear on the radio and r&b/soul. So I got a lot more in my ears than most people when they went through childhood.
I've listened to a lot of rap and the same thing applies...some I like, some I don't. Doesn't mean I don't diss a whole genre of music, it ony means I might not particularly like to hear a certain song in it.
As far as music in general, you can either go into listening to music with closed ears (it sucks I don't like it...turn it off) or open ears (this isn't what I'd normally listen to, but I can see where it was all put together), it's all up to you.
Fiev.