On the other hand, don t be impolite. You re human, so admit it. Treating foundation officers as peers means acknowledging your discomfort and mistakes. You should present your organization in the best possible light, but it s also important to tell the truth about your errors and the obstacles you face and your strategies for overcoming them. At a basic level, this means proofreading your letters and proposals, spelling names correctly, keeping track of who works at which foundation, and so forth.
Professionalism also means treating everyone with courtesy, regardless of their job title or status.
I understand the frustration with the concept of gatekeepers, but if you get to know the administrative people well, a lot of doors will open for you. Accept defeat gracefully and move on. Professionals file their rejection letters and move on to the next funder or the next proposal. In researching my book, Grassroots Grants, I was amazed to learn that some grantseekers actually dump their frustration on foundation staff. Complaining is a big strategic mistake, since you might want to approach the same funder in the future.