Hey, the site has over five million members! Even if only one in a hundred is a psycho, that gives you a mindboggling number of 50 thousand potential nutcases.
Does Chess Attract Angry, Mentally Unbalanced People?

I don't think chess attracts mentally unbalanced people. I do think, however, that chess provides an environment where people may end up showing the ugly side of their personality (namely losing games one had an emotional attachment to for whatever reason).

"chess provides an environment where people may end up showing...."
this should read "internet blitz and bullet chess is essentially an online video game, in such contexts people talk tons of psychopathic trash to each other."
it has nothing to do with "emotional attachment" either. this is just how many people normally behave when it comes to online video games.
(although I personally don't understand it, I wouldn't ever react in such way in regards to something as trivial as a video game. it takes a hell of a lot to get me angry, you'd basically have to launch a massive propaganda disinformation slander defamation campaign and/or threaten my life in some way)
Yes I could've just as well said that. But in my opinion it has everything to do with emotional attachment. If you wouldn't care about your chess games at all (= no emotional attachment), why in the world would you get upset about losing them? (Note that I'm not taking into account trolling, which is not what's discussed here.)

but it's a mistake to think that all those people who leave ridiculous notes to each other have some significant emotional attachment to their blitz and bullet games. this isn't really an appropriate characterization of what is going on there. it's basically, for the most part, young males talking trash to each other just how they would in any other gaming context. it's very strange to say that these people are "emotionally attached" to these internet blitz and bullet games. it's not exactly the truth.
Okay this last comment of yours makes me believe we're actually talking about different types of comments and situations. You're right in your own context, of course. In the trash talking young males scenario it very likely has more to do with hormones (which could probably be said about anything at that age) than anything else. I'm not a doctor or such, though, so I don't claim to know much about that.

"I tend to look at this website as a community of people you're trying to learn from and get along with. Maybe this is naive of me."
Maybe I'm naive, too, Congruity, but I believe this is the only sane way of seeing things. We need to foster this point of view! In another topic, (what should chess.com do with the king of trolls) someone asked me: "are you trying to learn here?" As soon as possible I'll go back to that topic and answer: yes. Here, there and everywhere, always. And consider that I'm 64 years old. Congruity, "congruitulations!!!"

I'll add my two cents...
If you've ever played blitz chess in any busy city park (such as Washington Square in NY or Dupont Circle in DC), you've heard a LOT of trash talk. If you merely listen to the words, some of it sounds downright nasty. If you look at the players' body language, however, you'll see it's obviously mostly tongue-in-cheek, and there's a lot of laughter happening too, because — admit it — a good zinger is pretty funny, and in a competitive, adversarial environment, they come pretty naturally. Once the game is over, the trash talk is quickly forgotton.
On the internet, you lose vital context. Furthermore, you have a written record that doesn't disappear into the ether as readily as speech. Now I'm not saying that some of the things people post truly ARE repugnant, but the vast majority of players here — even the ones that do trash talk — are no more "mentally unbalanced" (or even "emotionally attached") than you or me.
It seems more likely to me that online chess attracts easily-insulted players who can't just delete the offending comment and get over the "burn" of a comment that has already been forgotten by the "offender."

I'll add my two cents...
If you've ever played blitz chess in any busy city park (such as Washington Square in NY or Dupont Circle in DC), you've heard a LOT of trash talk. If you merely listen to the words, some of it sounds downright nasty.
True! The ones I remember are:
"I've seen this move before"
"You think I'm dumb?"
"I see what your're trying to do"
"Hey, this won't work!"

what? we are both, I thought, talking about the obscene notes people leave to each other as a result of internet bullet and blitz games? is this not the case?
confused.
Yes, but it seems to me that you're talking about people who leave them not because they're in fact angry, but rather for other reasons. I was talking about the other cases, as in the cases where - as the OP seemed to suggest - people leave these comments because they get angry or otherwise.

What do you mean by, "Does chess attract angry, mentally unbalanced people?" What kind of question is that? Do you think there's something wrong with being angry, huh? (Pokes a finger in OP's chest). So you think you're more mentally balanced than I am, huh? Do ya? (Pokes OP's chest again). I'll show you who's angry and mentally unbalanced ...". 
it is a fair comment. i was once diagnosed as unbalanced as an 18 year old. my chess is angry attacking chess, although i have tried to calm it somewhat. i have been angry and frustrated most of my life, kind of ugly duckling syndrome, if i want to flatter myself that is. most people would not want to talk about their demons but i have no qualms about discussing it. i spent time at 3 different schools as a teenager, half of it playing truant. then we had 4 grades in the last term A B C and D. i managed to finish in the A Class despite my sometimes volatile behaviour. at playtime we all wanted to be out as quickly as possible to play foota. one day we had an english exam in which we had to explain the whys or wherefores of what a certain character was thinking of when he did something in this book we were supposed to read. when the bell went everyone bolted out the door and i was told to finish the paper. when the teacher walked out of the class room, i tore up the exercise book, poured ink all over it and threw it on her desk, no way was i going to miss a football game at playtime. but there u go, it is all a long time ago, i am a pensioner now so what the heck. i aint got any plans to blow up the world or portray myself as DR EVIL, ahahahahahahahahahahahh
Is the world normal. i certainly think that in this country uk, things are not normal. the gulf between rich middle class and the poor is widening every day. i like many other people have worked for most of their adult lives and still end up at the poor end. when i watch some tv programmes like cash in the attic and escape to the country, and the apparent wealth of some of these people, i wonder where i went wrong.what has this to do with being mentally unbalanced or angry. dont know. how do we think, what do we think. i certainly have a 5 star hate against teachers. women teachers that is. probably based on my experience at school and all this rhetoric about getting better results from pupils. the fact remains u cannot make a person who is not intelligent==intelligent, so in reality the same percentage of pupils will get good results as they always have done because they can do the work with very little study.

Hey...of course it attracts these unsavory characters.
It's about imposing your will on the opponent.
Completely demolishing your opponent. Utter destruction.
Taking complete control and calling the shots, dictating the tempo.
How could it not attract those with a lust for power?
And speaking of unbalanced...didn't you read "How to Reassess Your Chess 4th edition" where the author speaks of...
imbalances as strategy?
Smh, some people's kids. Just kidding. Yeah, I've encountered someone who insulted my mother.
Of course, this was before I promptly checkmated him and told him to get lost.
We all hate losing. And sometimes it feels like we let games get away from us that we shouldn't have. Heck, sometimes simple bad luck leads to a victory for the opponent.
That said, what is up with all the nasty notes people post on others' "About Me" profiles? A quick tour of many players' profiles in the, say, 1200-1600 rating range will reveal some of the nastiest, meanest, quite frankly mentally unbalanced comments you're likely to find anywhere on the web... save maybe controversial videos on YouTube.
As someone who works hard to not take his chess too seriously yet works hard to learn from others and improve, I'd love to hear your opinions on this. Is the dual, head-to-head competitive nature of chess a catalyst to hostile, mentally unstable behavior?
I tend to look at this website as a community of people you're trying to learn from and get along with. Maybe this is naive of me.