I can't say whether or not this is true of Bustamante, but his continued support of this group is a big red flag.
I knew of the Aztlan movement for years before this issue hit the press, but did not know the Lieutenant Governor of California supported it.
What I don't know is how much he supports the insurrectionist aspects of the MEChA agenda and whether or not that support extends to using his office to further MEChA goals. Certainly, in light of the politics surrounding illegal immigration in California, this is an extremely relevant thing to want to know about.
While I do think some of the press surrounding MEChA these days is overblown, not all of it is. There is a fire behind all the smoke. Also, the "reconquista" movement is not limited to MEChA, and deserves some research and analysis as a whole, but MEChA is not a bad place to start.
Unlike some of the less-informed contributors to this thread (cough, *PRND21*, cough), I think it makes sense to find out more about this organization, what it is doing now (it is a national movement with chapters throughout the U.S.), and what it plans to do, in greater detail.
Bustamante notwithstanding, any group which has the goals that MEChA has publicly espoused is worth keeping track of.
Again, what have they accomplished? Why do you fear them?