A lot of the issues we have with other players in game, mostly boil down to the same thing. Their attitude. For example:
- People that get a certain dungeon they don’t feel like doing, they will either AFK, Leave or intentionally cause grief within the group.
- People who force a “speedrun” on the group without verifying if that’s ok with everyone else, or pull when the group isn’t ready for it.
- With the slightest slip up, you can get called out with the most vulgar language you can think of (sometimes even threatened).
- Or, if you want to point out something (friendly or no), you will be answered with childish behavior (like “Gitgut”, “n00b”, “get a life” or even a “Please uninstall the game”) or more vulgar language.
- People who join farming parties, expecting a clear (or simply wish to be carried) without asking for their permission/informing them.
- People who create farming/clear parties and mention within the PF description that only experienced player may join, expecting a clear they haven’t gotten themselves yet (or simply wish to be carried).
- People excluding or calling out others, simply because they are not wearing the BiS gear (even for something as Hard Mode trials).
- People who wear crafting gear or gear that does not suit (think strength gear on a healer) the class they are playing and refuse to equip the proper gear for their class & level if the party asks them to, simply because they want to spiritbond the item.
- People who don’t bother with mechanics, but simply want to burn down the Boss and thus completely ignore all of the mechanics.
- People don’t feel like sticking around after a group wipes during a trial, even if the situation is perfectly salvageable but will require a bit more effort.
These are topics which can be found on the first page of the general discussion of the official forums on a daily basis. It even reflects on the replies you see within these threads as well. There are plenty of other examples you can think of and most of them would apply in both ways.
It’s like we, as human beings, forgot how to properly communicate with one another, respect one another or work with one another. It’s all about “Me” and the rest can either do it “my way” or take “the highway”. 
We, as a community, decide what the community is all about. So, only by actually talking to one another in a respectful way and treating each other as equals, can we even start to hope for a good community. The thing is, this does not only apply on this game, but also in other games as well as in real life. 
“Treat others how you like to be treated yourself”