I agree with you. I think some of the rock fans who bash rap and hip hop do it mainly because of ignorance. They make harsh generalizations about it based only on what they've seen on TV and heard on the radio, and they don't understand the kind of effort and creativity that goes into good hip hop. Like you said, in most cases, the electronic devices rap/hip hop producers use serve as instruments. Besides, if songs created using electronic hardware or software aren't worthy of being called music, then techno, electronica, and a lot of music from the 80's isn't music either. As you said, some rap/hip hop artists do use instruments. Fat Jon (aka - Fat Jon The Ample Soul Physician; piano/keyboards), The Roots (drums, guitar, bass guitar, keyboards), Nicolay (keys, guitars, bass, drums), J Dilla (aka - Jay Dee, who played 20 instruments), and many others have all played their own instruments at one time or another. As a matter of fact, more and more rap/hip hop artists are using more traditional instruments in their music nowadays due to the legal red tape associated with using samples.
And to the non-believers who're still thinking "it's just pressing some buttons on a drum machine," check out this beat making video from a French producer named 20SYL:
http://www.youtube.com/watch?v=8OhDC5GUJYw
Like producer Kev Brown said in one of his beatmaking videos, "Don't get it confused. It's not just loopin' up some stuff and callin' it 'the sound of the culture.'"
Also, these same people are not aware that not all rap/hip hop is about "the club," sex, drugs, money or murder. That mainstream stuff we're force fed on a daily basis is only one facet of the genre; the underground circuit is where most of the variety and substance in rap/hip hop music is. And those who think that good rap/hip hop doesn't take any effort to create are dead wrong. Sure, anyone can talk over a cracker jack Casio keyboard beat, but not everyone can be an emcee (and for the record, yes, there is a difference between a "rapper" and an "emcee"). Being a good emcee is equivalent to being a stage poet. You have to have a very extensive vocabulary as well as a fantastic handle on language (i.e. - synonyms, antonyms, homonyms, etc.). You have to be familiar with similes and metaphors. You have to have confidence and stage presence. You have to have good delivery. You have to have a great memory (and if you freestyle, you have to think quick on your feet and be able to adapt). And on top of all that, you have to have a sense of rhythm so you can recite it all to a beat. The same complexity and effort also applies to any good producer. There's a lot of trial and error, fine tuning, technical know-how and musicianship that goes into what they do, besides the fact that they have to work in tandem with the artists who sing or rap over their tracks (and I know first-hand - my husband's a producer).
So in short, most of these bashers need to do some actual research on hip hop before making generalizations and jumping to conclusions.
Just my two cents.