There are two factors at work, here, and it is important to consider both.
1) The obvious one is the “La Raza” element. The tendency is to put the emphasis on this, but that is a flawed assessment, because there is a lot more at play in this situation.
Primarily, it is important to remember that the MM is indeed a “Mafia”, and as such is larger and far more organized than a typical street gang. Their intent is to make money instead of any Raza nonsense. In past, they have had to intercede with street gangs, particularly the Crips and the Bloods, to *halt* their war, because it “was bad for business”. And the street gangs realize that the MM is powerful enough to wipe them out entirely if it chooses. The war quickly ended.
But California is rife with gangs, and has been since the days of the Barbary Coast. At times these have even included vigilante organizations. (It must be in the water or something.)
http://en.wikipedia.org/wiki/Category:Gangs_in_California
2) The anti-black racial element. This cannot be ignored and is very obvious, because the MM and Mexicans as a whole *do not* try to drive out any other ethnic groups(*), be they white, Asian, Indian, etc. Importantly, for many years they tried to coexist with blacks, but over time have reached the conclusion that as a group, the behavior of blacks is intolerable.
And this fact is both ignored and disregarded by both the media and the government, which are horrified by even the suggestion of “logical” racism.
(*) Importantly, Hispanics do not intermix with Hispanics with different nations of origin, and will self-segregate, though generally not with hostility. In the western US this means for the most part that Mexicans do not share neighborhoods with Guatemalans. To each their own. Intermarriage between different Hispanic groups is very rare. A considerable irony, since Mexico is extremely heterogeneous ethnically as well as linguistically.
Liberals have tried for decades to create a coalition of “everybody vs. whitey.” The whole idea behind the notion of “people of color” being a coherent group.
Others have pointed out that the real racial divide in America has always been “everybody vs. blacks.” IOW, “people of pallor” is much more likely to emerge as a real grouping than people of color.
The ruling elites of Mexico are predominantly of European Spanish descent, with little mixing of the native population.