We shall see.
The reason people were better in past MMOs was that your reputation was everything. There were no name changes, no server transfers and the time it took to get your character to the top levels was in the months not days/weeks as it has been with the current MMO crop.
Its my hope that Enmasse does not allow transfers or name changes .. that will solve some of the issue. And much as I dont really care for the RNG nature of end-game here (Enchanting end game gear etc) its my hope that the amount of effort involved will make characters value thier reputation more and more.
Bottom line .. if its easy to reach endgame (roll an alt) or there are transfers / name changes available .. the community will be horrid. Remove these things and make end game either a true grind or a real group event (I prefure the latter) and your reputation becomes more and more important. Once your reputation is of value ... attitudes change.
I see it more as the end result of 20 years of 'Self Esteem' teaching. Now too many people have been convinced that they're the Golden Child and that the world will work to their desires, and have the attitude to match. It'll get worse before it gets better; it's always darkest right before the storm, after all.
TLDR: At bottom.
Everyone needs to consider some of the things that everyone has said.
Like it being the internet. I cay say and practically do whatever I want and none of you can really alter my behavior. That's mainly the reason why people say so many rude and hurtful things online.
I like to think of myself as someone who is fair and generally a nice person. I am proud to be who I am and I really do think I am a kind hearted person. One of my friends did point out to me though that online in game I am kind of a jerk to people who I don't know. After thinking about it over and over I realized that I am not always the nicest person when it comes to online games. After you hear a question a good ten times an hour sometimes you might have some rude remark to the question.
I am nice to everyone that I meet in real life but maybe I am not so nice to people in games. Maybe I try to be nice as long as possible but people wear on me and turn me a bit bitter after awhile. This may be the case of the people with the classic and new(ish) "you mad bro" type of responses.
I wouldn't say that those people are exactly bad, but maybe were logged on for too long experiencing the same thing over and over and just sort of exploded like I admit that I do. I am happy to answer the same question asked over and over but eventually I come to a limit and just say something rude or silly as well. It's something I need to work on as a person but it really is the internet that gives me the freedom.
There are definitely rude/immature people out there that will get their fun by making you miserable. It can be by ganking lowbies, trolling chat to cause a problem or anything else that they know can make a person get mad.
The best thing to do is just ignore the hate and realize when someone types "umadbro" that they are really just trying to get a response out of you. As long as you don't continue to give the aggressor fuel they will give up on trying to make you angry. As soon as you give in and give them something else to respond to you have lost the battle. Look at it that way. You win by ignoring their comments and you lose if you give them the satisfaction of responding.
Also, don't respond to someone being hateful in a general chat. All it does it fuel that particular person to keep harassing you and encouraging others to join in. Just ignore it like it were a 4 year old talking to you. People have almost no consequences online and will take advantage of it.
TLDR: Just ignore people to attempt to tick you off, they will go away.
High fantasy games (more so the eastern variety with more absurd outfits + T&A) seem to have more immature or socially awkward communities I've noticed. When you move towards more moderate or low fantasy (Ultima comes to mind) or even sci-fi, you get different breeds of 'un-wantables' but I would argue they are less obtrusive to the community as a whole.
The real question is if there will be GMs to monitor and make sure that TERA doesn't become a babysitting service. As of right now I have noticed two MAJOR flaws with the game, and that is the community and chat filter. I'm still on the fence about buying and bringing my clan in but honestly if we don't see any responses on the forums of at least "We're listening" then count me out.
The community on any sort of PvP server is always callous. What do you expect? Everyone has been ganked and before long they realize that their only friends are the people within their own guild. Therefore, area chat is full of flaming, trolling, and whining. It's a glorious smattering of anger, revenge, betrayal, and hatred. Don't like it? Turn off area chat or go to a PvE server.
Also, because it is necessary - So mad, so sad.