I didn't know that Americans ever committed any sort of "genocide" against the Mexicans. The Mexican population is mostly of Spanish descent. The closest America came to a genocide was against Indian populations in the Great Plains. Even the Indian population of Mexico is different from the former Indian population of America. Most Indians in Mexico descend from Aztec origins. Thus, the American western lands never belonged to those same Indian groups that may or may not sneak across our southern border.
The Mexican population does have a semi-legitimate claim, I guess, to the American southwest, but, then again, they are the fair spoils of war. Texas declared independence from Mexico and willingly joined the US. Thus, Texas was every bit a legal acquisition. New Mexico, Arizona, California, Nevada, and Utah, however, were more populated by Americans at the time of the M-A War than by Mexicans. We won them in a fair and legitimate war, albeit declared under dubious circumstances, and, thus, they are ours every bit as much as Alsace-Lorraine currently belongs to France. Anyone in the American southwest who wants to leave the US and join Mexico is welcome to do it. I doubt many would want to live in the squalor of Mexico as opposed to the prosperity of America.
As for illegal immigration. No, Mexicans have not been granted acceptence in the American population because they are "light enough," as you put it. They have gained some measure of acceptence because our government does not have the backbone to possibly "offend" the Hispanic voting population of the southwest and send all the illegals packing. They should not be allowed across the border in the first place, let alone stay long enough to gain acceptence. I, personally, would gladly trade "cheap labor" for secure borders any day of the week, and without second thought. If they want to become citizens, they're just going to have to do it the legal way, like my ancestors did. Not sneak across a stretch of desert.
As for Spanish. I am against a publically bilingual nation. Yes, they certainly can speak Spanish within the confines of their own homes and in dealings with each other. I, however, a speaker of English (obviously), the language of our Founding Fathers (yes, I know there were some German speakers scattered about, mainly in Penn.) and our de facto official language for the past 225 years, should not have the uncomfortable feeling of trying to find my way around in a town in my own country with signs printed in a FOREIGN language. My ancestors, and almost all of ours, considering we all speak English on this board, either knew or had to learn English upon arrival in order to survive. Yes, they could use their native language when dealing with each other, but if they wanted to assimilate into American society (which they did; the new immigrants seemingly do not), they would have to learn English. I should certainly not be paying extra taxes because schools have to hire Spanish-speaking teachers to teach illegal immigrants who have no wish to learn English.