There is a rising belief among Mexicans that the Southwest, and perhaps the entire North American continent, rightfully belongs to Mexico, and was stolen from Mexico by the Europeans. They call this alleged territory of theirs Aztlan, a name taken from Mexican folklore. This is the argument of Mexican nationalist revolutionary groups Mecha, Aztlan and La Raza (translated "The Race," to which Supreme Court Justice Sonia Sotomayor belongs).
Many Americans mistakenly believe Cinco de Mayo commemorates Mexico's independence day, but this is not true. Mexican Independence Day is celebrated on Sept. 16. Cinco de Mayo is celebrated on May 5 and commemorates the expulsion of the French from Puebla, Mexico, in 1862.
So it becomes easy to understand why Mexican revolutionaries in the United States promote this holiday among their followers. They do it to set the stage to expel all the other "gringos" -- and, if California is to be any indication of things to come, African-Americans also -- from Aztlan. These revolutionaries are proverbially killing the geese that lay their golden eggs, and destroying the reason why so many risk so much to come here to begin with.