> I am an expert, you must listen to me, and you don't know enough to even question my direction
is going to be ignored.
It doesn't matter if this person is a designer, a coder, a DBA, or a networking person. That attitude just doesn't fir with open projects.
You need to become part of the project, make small suggestions first, and back up your suggestions with reasons for them to be implemented (not just "because I say so and I'm the expert")
Unfortunantly, many designers do take the attitude that other people aren't qualified to question their design.
This is not saying that they are being asked to be humble in the presence of the mighty developers, it's asking them to be humble in the presence of the established team, just like a new developer would need to be.