You just said that you need to be told not to rip aggro of MTs - and obvious mistake that you dont even seem to be aware off making. How are you supposed to improve upon those things if people dont tell you?
You also claimed that:
Which, as sorry I am to say that, you clearly were, if that report of the run is to be believed (and why shouldnt we believe it? You even confirmed yourself that you ripped aggro of the MT which isnt only bad play but also bad etiquette.)
So if you werent lying at that point, you were unaware of you making pretty obvious mistakes that you shouldnt make anymore in level 70, wether that content is a week or a year old.
I'm not trying to justify the insult you recived, I still think they should have handled the issue with just removing you silently. And while I'm not saying you deserved that insult, I hope you do realise that your poor and bad play got you into a situation yet again in which a party felt the need to remove you from a duty to clear it in an enjoyable way, because you're not able to do, because you dont communicate with your party and lack basic understanding of common "strageties (like: dont steal aggro) and how to play your class.
Sorry, if this thread didnt went the way you wanted to - with everyone telling you how terrible you were treated (and the treatment was infact not very nice).
But let me tell you that I'm asking the thread-question "What is it with people?" way, way more often about players who need to improve on very basic concepts in endgame content - "What is it with people that they've reached level 70 and still dont understand how a tank-swap works?" - "What is it with people who reached level 70 and still dont know to drop tank-stance when offtanking?" - "What is it with people not knowing how Shirk works and how to use it?" (...granted, that one is naive and wishful thinking).