It seems that I am going to have to disagree with many here and give a big raspberry to the "intimidate automatically fails." Many years ago in the Complete Fighter book, TSR gave me a quote I took to heart for all of my GMing: "don't say no, determine difficulty."
Should you be able to intimidate the noble? It may be difficult, even much more difficult, but it should certainly be possible. If the god of intimidation showed up and said a few words, would that still fail? If so, we're back to the system of immunities that have plagued D&D for a long time. The game designers decided to remove things like an immunity to flame for a fire elemental, why would they dream of putting them back in for a social encounter? Intimidate is a social skill, it's a social encounter, they fit together in a way that, say, acrobatics does not (although I wouldn't absolutely rule that out either).
Beyond that, I would argue that Intimidate is a VERY appropriate skill for use in negotiation with the nobility. It seems to work far better than diplomacy in most of the movies or books I've seen. Might a noble get a huge morale bonus in resistance? Yes, he most likely would, but as he isn't a construct, it should still have a chance to succeed.
Just my $.02.
--Steve