I don't think the topic is too far off base, maybe worded a bit dicey, but...
I wouldn't be surprised one bit if we had a civil war of values in this country. When you look at the direction things are headed, it probably isn't going to get any better.
I think rather than asking a question about an illegal immigrant uprising, it is a fitting question to ask what caliber for defense of property and life if society breaks down at some point. That breakdown could be for any number of reasons. Think about the riots in L.A., hurricane Katrina, the riots in France, and the conflicts in any part of the world. I think the question is what caliber for defending yourself, family, and property if need be.
For me it will be lots of magazines loaded with the good ol' .308, and a battle/assault rifle that is reliable to the end.