Dear michaelj
Sadat did not choose to called a 'pharaoh' instead of 'arab' as part of his personal or cultural identity, it was chosen for him by his critics.
In Egyptian culture, the word pharaoh is often used as a sardonic device to belittle somebody, Egyptian humour is often sardonic. For example, it is common to call a spoilt child 'pharaoh' or to describe somebody who thinks about things too deeply (or who likes to give that impression), as Socrates (or Sokrat in arabic.)
The idea of Sadat as pharaoh was probably secured in history when the man who shot him, Khaled el-Islambouly, yelled "Death to the pharaoh" as he shot.
If you wish, you can also find references to the current president, Mubarak, that refer to him as Pharaoh.