my credo is: there are 2 kinds of music: good and bad, whether it's rap, b/b, concerto grosso or medieval choralgrunting, I don't mind, as long as it's goooooooooood.

Wow... Let me talk for my age-group of classical "lovers". I am 16.
To start, I hate rap. Mainly because it's just a bunch of guys trying to rhyme random words to swear words. Honestly, a song with swear words every two lines is really unnecessary.
Also, there is no real melody, recurring melody, and all that stuff that makes classical music interesting. It's just synchysis over and over again (respectively).
Generation gap has to do with it, but it isn't the main difference. It's the style. I grew up to classical, and generally speaking there isn't much else I enjoy. Every now and then a modern rock piece will come out that I enjoy, but nothing more.

I liked Gangsta's Paradise, like, 15 years ago. Does that count?

I have no interest in rap, though I like lots of popular music genres. Rap seems incomplete to me, as so much of it seems to lack an essential component: melody. And where melody is found, it's often unoriginal (i.e., sampled or otherwise derived from previous dance music).

Another factor for me is my dislike of the aggressively macho posturing. I don't really relate to the cultural mindset or esthetic of rap at all; I don't understand the creative impulse behind it or the way it's rendered into a "musical" product.

I was going to reply to the Op, but Chopinist covered it pretty well for me, so I will just add my +1.

I also included two lectures on hip-hop when I taught music appreciation, and I did it to illustrate a point that Bartok made....

I have no interest in rap, though I like lots of popular music genres. Rap seems incomplete to me, as so much of it seems to lack an essential component: melody. And where melody is found, it's often unoriginal (i.e., sampled or otherwise derived from previous dance music).

Another factor for me is my dislike of the aggressively macho posturing. I don't really relate to the cultural mindset or esthetic of rap at all; I don't understand the creative impulse behind it or the way it's rendered into a "musical" product.

Hip-Hop has driven technology (sampling and looping) and even has some Avant-Garde artists trying some rather interesting things. (Jay-Z's Black Album, for example.)

(Remember, some people disliked Beethoven's music during his lifetime, thinking it little more than disagreeable noise.)

I don't listen to a lot of hip-hop, but I grew up listening to a lot of Run-DMC in the 80's, and I also like some of what Busta Rhymes and Eminem have done.

I also included two lectures on hip-hop when I taught music appreciation, and I did it to illustrate a point that Bartok made.

In Bartok's work on ethnomusicology, he discovered that music is an inevitable result of culture. People are bound together and derive their identity not only from language, religion and shared history, but also cuisine, fashion, literature (stories), art, and music.

Hip-hop is a wonderful example, and over the years, it has evolved much like most other kinds of music. It began in Brooklyn in the 1970s as DJs for block and street parties began talking over the music and manipulating turntables to keep the party going. It was positive and community-oriented, and was mostly unknown outside of New York.

Then, certain artists began to find a wider audience, and others became interested. Hip-hop was adopted and adapted by others, most notably the west coast (Public Enemy, N.W.A. and the beginning of "gangsta rap.") As hip-hop became more widespread, it was also borrowed by other mainstream artists (Run-DMC's collaboration with Aerosmith, for example.) It also spread across race boundaries (think Vanilla Ice and Eminem.) Hip-Hop has driven technology (sampling and looping) and even has some Avant-Garde artists trying some rather interesting things. (Jay-Z's Black Album, for example.)

Hip-hop is also more than a musical phenomenon. The culture also encompasses art (graffiti, which has become increasingly accepted in the fine art community) and dance (breakdancing, which evolved into hip hop dance and crossed over to Broadway with Stomp and Bring in 'da Noise, Bring in 'da Funk.)

Much of this mirrors developments in classical music as well. Classical musicians have adopted the music of the far east (Debussy's Pagodes and Rachmaninoff's Orientale, and contemporary composers like Tan Dun and Chen Yi), gypsy music (Albeniz, Falla, Turina), and Latin American music (Villa-Lobos, Ginastera.) Classical music has a variety of associated dance (from Viennese waltzes to the ballet traditions of France and Russia.)

Classical music has also crossed over into popular culture (think Bugs Bunny), and popular culture has always exerted an influence on classical music as well. (From the quodlibet that closes the Goldberg Variations to Brahms's settings of folk songs for the choruses he conducted to Horowitz's Stars and Stripes Forever.)

There's no denying that Hip-Hop has a strong effect on the ears of many, both positive and negative. No one is required to like it, just as no one is required to enjoy the music of Liszt. Some do, some don't; that's just the nature of music.

But like it or not, Hip-Hop is a valid artistic phenomenon. Whether someone likes or dislikes the message or sound is besides the point. Lots of people dislike the message/sound of Schoenberg, but that doesn't invalidate his place in history or the influence he's had. One need only leaf through Slonimsky's Lexicon of Musical Invective to discover that it is very easy to find severe criticism of any artist. (Remember, some people disliked Beethoven's music during his lifetime, thinking it little more than disagreeable noise.)

Hip-Hop has driven technology (sampling and looping)

I completely disagree with you. I believe that rap does indeed have a melody; it just depends on the perspective in which you listen to it. About the macho posturing, I disagree with that as well. I think you generalized that aspect of some rappers for every rapper and that is not correct. There are many rappers I like who do not portray an overly-macho personality.

Hip-hop artists certainly didn't invent the technology. The groundwork was laid by pioneers like Varese and Dodge. But many of the tools used in hip-hop and by DJs have created a market that wouldn't have existed otherwise.

If the technology exists to make music without devoting yourself to an instrument and taking the time to learn it, people will use it.

Just to add one minor observation in the same vein as Kreisler's first post (which I believe is spot on), another thing that seems to be shared by most new and temporarily unfamiliar types of music is the accusation that "it's not music, it's just a bunch of random noise".

Chopinist, all I can say is:
"Disco s..."
"Disco su..."
"Disco surely is yet another example of a legitimate and innovative musical genre."

Jim