A very interesting question. I believe there was anti alien feeling growing in the Republic due to the fact that many of the Separtistists were non human. Sidious had a talent using people's emotions. He used this anti alien feeling and the worlds of the Separtistists to further his cause. You can view all the films and noticed there are anti-human and anti droid prejudice. How many non humans are Imperials? Look at our own history. Did not Adolf Hitler use feeling against the Jews to further his cause? He looked for a scrapgoat to blame Germany's problems and found one. As to Mace Windu - Windu has many years experience on the Council. Very attuned to the Force. Was I mistaken or did Mace actually take up for Anakin at one time during ATOC? Intolerance was a very ugly part of the Empire.Intolerance aided in keeping beings subjugated.