Are there shows more susceptible to attracting terrible fans?
 

(This is a serious discussion. I'm not ranting, or accusing anyone. And regarding the examples I show bellow, they are by no mean represent the entire fandom of any show)

You must have heard of, or experience it yourself, the terrible fandoms that are Tokyo Ghouls, Hetalia, Attack on Titans (in the West, their equivalences would by My Little Pony and Undertale fandoms.) These obsessive and uncivilized fans, they bombarding you with memes and rantings, slipping their favorite shows in every discussion instead of context, and might even harrass you for not sharing their opinions.

Is there something commons with these shows, howevers? Are these shows acting as beacons for all the sadistic, nihilistic, obsessive, and purposeless people out there?

In my opinion, yes. As you can see, the bad things committed by these fandoms all came from small groups of fans who considered themselves elitists, the only people who understand all the nuances of the shows. They've elevated their favorite shows into something almost holy, something that codified themselves as people.

Conversely, the show must be able to establish a distinctive culture surrounding it to foster these elites. It must be different, not original or popular, but just different from its contemporaries. The idiosuncracy could be in the theme, the story, the art, the voice acting, etc. Bonus points if these shows have theme that resonnate with the darker part of people, like racism, sexism, nihilism, atheism, etc.

Being debatable is another good way to have these elitists, though it is not always the case. This normally means that messages the show implies are debatable (This is more likely to occur with the social-minded American cartoon, such as the equality message of Steven Universe, or the nihilistic preaching of Rick and Morty.) The show should create stong opinion on its fan in this case - you either "it's terrible" or "it's great" instead of "meh."

That is my opinion. What is yours?

No. Maybe you just hang out with terrible people. Or, in a twist, you are the terrible person and the others want to make you go away.
Looking at this thread my bet is on the latter.

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Frankly, when a show as harmless as My Little Pony can generate elitists and other forms of bad fans, I believe that any show has the potential to generate bad fans (except when the show has no avid fans). Heck, even company brands can generate elitists douches. Just see the flame wars in net forums between avid Nintendo fans, PS fans and XBOX fans. There are also battles between Apple loyalists and Samsung enthusiasts in various tech forums which sounds dumb but it's real. And the less we talk about Marvel vs. DC-fans the better.

Still, I’m just grateful that the good fans still outnumber the bad (but vocal) fans.

It’s just like life: there are bad and good individuals in it. That applies practically in every place where a (large) group of individuals gather. Also, elitism (and other negative traits) can be triggered by practically anything as long as there are social interaction.

There are good people and terrible people in fandom of almost any anime... I don't see the point of this thread.

To the OP.. just watch some nice anime and move on. :)