When I see people destroying things while waving another country's flag (and the Prez of their country (Mexico) endorses them), the proper term for them is "an invading army". Is there any doubt in any sane person's mind about how a country should go about defending itself from an invading army...
You know, as neat as it may sound, I wouldn't want to build a time machine, "Why", you ask? I'd hate like heck to go 20 years into the future, come back, and have to tell everyone that there still haven't been any arrests...