Banging head against a brick wall

I feel sometimes like I am banging my head against a brick wall. Our intranet menu plays host very frequently to the "I'm more powerful than you" playground contest. Pressure is put on the intranet team to add new top-level items to the menu based upon a department's "importance". Those putting the pressure upon the team are impervious to any clear explanations of user-focus or findability - our job - and generally try to assume an "I don't care what you say, I'm more important than you" attitude.

We have tried a number of ways to improve this situation: concerted communications efforts and - a measure which has been partially successful - user-focused card sorting exercises, which do deliver some form of "scientific proof" to those higher up the ladder that no-one thinks departmentally (apart from them!). Does anyone else have any experience of this specific problem, and have any useful suggestions for resolving it?

Contact me if you have any suggestions