the existence of different types of people, who have different beliefs and opinions, within the same society

After years of state control, the country is now moving towards political/religious/cultural pluralism. 政府多年控制之后，该国正走向政治／宗教／文化的多元化。

the belief that the existence of different types of people within the same society is a good thing

They are committed to human rights and pluralism. 他们信奉人权和多元主义。