When White plantation owners from the South moved to the southwest, in the 19th century, the Mexicans living in the Southwest had their culture suppressed by the Whites as part of the process by which the dominant culture was established.

Blauner hypothesis

Explanation:

The popular hypothesis called the "Blauner Hypothesis" states that minority group or communities that are created by colonization, since it is forced on them, are prone to experience a superior degree of racism and discrimination more than those that were created by voluntary immigration.

The minority groups established through colonization will face greater, more long-lasting shortcoming and oppression than the immigrant minority groups.