Why is Leo disgusted by the script Max chooses?

The script that Max chooses is called "Springtime for Hitler." Not only is the musical itself horrible, it is meant to show a good side of Hitler. Besides the fact that Hitler is one of the most reviled men in history, Leo and Max are both Jewish. In order to procure the rights to this script, Leo will have to swallow his distaste for Hitler and hide his ethnicity in order for it to work.