Because you did not make the rules, you did not make the group. In what standards do you have a right to tell others how to play in said content?
The game itself made that group for you and the game does not have an standard by what skill you need to be in that group. If I wanted people to play by a set standards, I would make my own group and make sure people knew what they are. Both sides can say the same thing about each other because of that. If DF had a standards that all players must follow. You than would have a right to tell people to be at it.
It is that simple. What you are saying about public interactions the other side can say the same to you about. Both sides are willing to run over each others fun. it is a no win type deal for people who want them to get better.