Yes, 'smooth jazz' is not jazz.  Congratulations to the author for pointing that out.  You can almost say that the reason that smooth jazz is hated is because it is so innocuous.  It is the shit that you hear in the elevator, but it is also the shit that makes me not want to murder the asshole that just cut me off in rush-hour traffic.  Back off that shit.  It is the glue that keeps me together when I make it to the office an hour late because everyone driving by the wreck had to take a good, hard look at it.  Of course, I choose my smooth jazz carefully.

Finally.  He discribes people that decry that they 'like all types of music' by saying that they are people that really 'don't care enough about music to have an opinion about it.'  I'm fucking sorry that I don't care if it is classical or nu-metal.  If I detect artistry in it, I like it.  I am genuinely sorry that I am not an over-opinionated prat that feels the need to answer the question, "So... What kind of music are you into?" by listing fifteen genres and claiming that all other music is crap.

I think he bullseyed you in that section and it struck a nerve.  No offense, dude, but you can't listen to smooth jazz on purpose and have strong opinions about music.  No that there's anything wrong with that.  Some people like vanilla and some people like rocky road. It's not a big deal.

I don't think System of a Down deserves to be saddled with the responsibility of all of nu-metal's crimes, though.  Of all the bands that get labeled as such, Soad does the most to distance themselves from the pack with pure innovation and inventiveness.  Guilt by association isn't adequate, because they do kick quite a bit of ass when they aren't busy soapboxing.  Even then, they tend to kick some.
If he's going to pin the swarms of copycat bands that emerged under the nu-metal banner on anyone, it should be Korn, considering they launched that whole sound.

Every other point he makes is completely accurate, if so obvious as to go without saying at all.

Oh my Christ. I would rather listen to crunkcore and whatever Brokencyde are, 24/7.

That would be crunkcore.

So nothing's wrong about Gangsta Rap with the music itself, it's really just how the people who listen to it present themselves as total douchebags because they are too busy trying to offend people? And that's why it's on the list of some of the most hated genre's ever?

Can't say I've ever cranked up Wu-Tang Clan in my sunbaked 1995 Ford Taurus while trying to deliberately piss people off.  Especially since I still have the handicap tags on it from the previous owner; my grandmother.

even if it did thump up and down the street, would it really matter what music I would be playing in order for it to be considered annoying at that point? Any genre that loud, from the Magic Flute to African drum solos featuring Lil' Wayne, can be annoying. Do most of the people who blast their music choose Hip-Hop/Gangsta Rap? It seems so, but I don't think that it warrants to be a "Most Hated" genre. In my eyes, at least.