There is no intolerance to highlight. You are pretending there is. No one ever said it should be a "white person" representing the USA exhibit (NOT "AMERICAN" EXHIBIT). It is reasonable to assume the USA wouldn't be represented by an Asian, since we are not in Asia... is that "racist" or "intolerant" of us to assume that? How about an Italian person? Would they be a reasonable representative of the USA? Or how about an Irish person? There are certainly more Irish and Italian Americans than Mexican Americans, aren't there?
My personal choice would be a Native American... wouldn't that be the most appropriate representative of the USA? Or maybe someone who had a plethora of ethnicity and heritage, to the point you couldn't really distinguish what they were? Would that be a suitable symbol of the 'melting pot' of America?
Mexico is not yet part of the United States of America. It is peculiar and odd to have a person who is Mexican, representing the United States. Just as it would be odd and peculiar to have someone from China representing Mexico. I am sure there are SOME Chinese people living in Mexico, somewhere... and they are just as much Mexican citizens as everyone else, and it wouldn't be inappropriate or racist for the Mexican display to not have a Chinese person as a representative. It wouldn't be racist or intolerant for Mexicans to complain to Epcot about that.
But now... what YOU want to do, is claim that is what this is about... discriminating against Mexicans! As if these people were offended they had to look at a Mexican person at Epcot. ---Let me just say, having been to Epcot... you do not feel as if you are in the United States of America. There are people from every corner of the world there, every day. As a typical white American, you feel very much in the minority. So the idea that these people were somehow intolerant of anyone other than white people, goes beyond the kind of ignorance usually associated with this kind of bigotry. It's a much more simple-minded ignorance of culture and reality of the world around them.