An inflexible attitude about a particular group of people rooted in generalizations and stereotypes. Often unchangeable "All Irish are drunks", "All Mexicans are lazy"

Prejudice

Explanation:

Prejudice is a way of thinking about a certain group of people based on the stereotypes about them. The groups can range from racial groups, gender-based, and even political affiliations. Prejudiced thinking is commonly negative and is usually not based on rational thoughts. It is often used as a way to create in-group/out-group distinction and has often been used to justify many atrocities in the world.