There was this excitement and controversy that was really an expression of the kinds of passions that differences of aesthetics and political opinions, and taste could give rise to.

1. that was really an expression of the kinds of passions 是 this excitement and controversy 的定语从句，把 this excitement and controversy 视为整体单数处理，that was （关系代词 that 作从句主语，be 用单数 was）

2. that differences of aesthetics and political opinions, and taste could give rise to 是 the kinds of passions 的定语从句。关系代词 that 在从句中作 give rise to 的宾语。理解方便，把它换成 cause （引起；导致）。

3. an expression of the kinds of passions：对各种激情/情感的表达。

4. differences of aesthetics and political opinions, and taste 是第二个定语从句的主语，并列关系。