There are always players who seek the way of the least resistance. If you have choice to get carried or to wipe several times till all players learn the fight, which one would you take? Some don't consider lying their way in farm party to be immoral.

In situations like these the game developers have to create features to prevent such behaviour. Imagine how would the game look if there were no item level requirements at all... not saying that these are sufficient.

Basically if the community can't prevent misbehaviour on its own then it is time to create restrictions or give players tools to filter their PF members.