Is it normal that people you hate always happen to like a certain genre

Well, I guess you hate me now, don't you? :)
Haha, jk. I'm well-rounded musically (aka I like everything except rap and dubstep). But to answer your question, it's normal, I guess. A lot of people that listen to metal are usually depressed and hard to hang around (Example: a lot of hardcore is darker than most other music.) If they listen to power metal, however, it's not nearly as bad. Most power metal stuff (aka Dragonforce, etc.) is very upbeat, usually covers of pop songs and stuff only with distorted guitars and the like. But a lot of people who listen to metal are screwed up. Some are lucky, but the people who let themselves go make up about 85% of metal listeners. You're probably better off not liking most of them. :) Just my two cents on that.

And like most others have mentioned, there are a TON of different types of metal. You can't generalize them all because they are very distinctly different. Power metal, as I mentioned before, is very upbeat. The Cores/Screamo are typically very dark, although there are a few exceptions such as I Set My Friends On Fire and We Came As Romans. Heavy Metal can differ, but most songs are ballads in form of complete mayhem. Black and death metal.....do I need to go into detail on that? Now dubstep is the biggest craze out there right now, and i flippin' hate it. But that somehow is a type of metal, and most American teens listen to it now. So don't assume just because it's a type of metal that it's instantly Satan or something. A lot of metal music has an amazing point or meaning behind it.

Generalisation, don't even go there...

Many people i talk to on the internet seems to only be interested in one genre and bash all the others by saying they are not "real music" they have no idea what they are saying.

Narrow view for you right now. You'll grow

You'll never see a nice, clean busyness man walking around with ICP in his headphones. There is truth in some stereotypes.

I think certain types of music appeal more to certain types of people, it's just natural. A lot of it has to do with your upbringing, your social group, the 'image' or brands associated with that genre and the entire subculture behind a genre.

Most of the people I know who are into Metal and Screamo have similar personalities and interests. They style themselves similarly (long hair, beards, black band t-shirts, piercings, tatts), they tend to be middle-class, white, male, they tend to have similar personality traits, they idolise guitarists and technical playing ability. I think this indicates how crucial the subculture attached to a genre is in determining its following.

Would Metal and Screamo appeal to the same demographic if it was performed almost exclusively by black women? It's funny to imagine, but if it sounded exactly the same, do you think all those long haired white teens would be buying their albums?

Of course the stereotype doesn't reflect the entire audience; many people I know who have eclectic tastes in music don't neatly fall into a box or category of person.

Hmm I love Metal and all types of it, Rock and Punk and Electro like Dubstep, Techno, Trance or House and occassionally some Rap!

But not all Metal fans are same you can't generalise that...

I can enjoy this type of music quite a bit, but I do agree that a large amount of the fans of this type of music can be pretty big douchers. They take the anger part way too seriously and miss out on the lyrics and music part. The ones that really get me though are the ones that think they are bad ass and start fights, please. (i realize this is a quality that cannot be generalized to all metal and screamo fans, just a certian portion)

I don't really care for screamo, but there is some excellent metal music out there.