I hate to sound like an arrogant or pretentious bastard but I'll just go ahead and say it.
A lot of you have to realize or maybe learn that, although I don't agree with that guys list, some of those films(not all, Darkman for example) are somewhat horror films like Sixth Sense or Silence of the Lambs. Movies aren't always straight forward.
A great example is how there isn't just comedies or romance films but RomComs as well. Just because a film doesn't have some slasher villian, zombies, werewolves, vampires or something else that goes bump in the night does not mean it's not a horror film.
The Sixth Sense and Silence of the Lambs do have enough elements of horror in them to qualify. Yes for the most part they are more of a suspense/thriller but that doesn't exclude them from also being in the horror genre too.
I've had this argument with a lot of people in the past on and off the internet and I think too many people have a narrow view of what dictates 'horror'.