And why can't an arbitrary set of genetic and cultural traits have a name? Everything else in this universe can be broken down to an arbitrary set of something. Why for e.g. call somebody an American when it's only a person living withing arbitrary lines on map?
I'm sorry but that is a really weird argument. Who are those groups of people who want us to pretend there are no similarities or differences between them and other groups of people?
Calling it "pretend" is both dismissive and begs the question. The people you want to call "Hispanics" are ethnically rather diverse, far from homogeneous. The similarities you see originate in ignorance. Mexicans aren't Columbians, Brazillians aren't Portuguese and all of these countries are home to many different ethnic groups with their own histories, languages, cultures and genetics.
At the very least, representation in government. People who share my ethnicity have unique social problems that don't apply to any other "race". I don't need a race, but the people who share my background need to be discernible on a census.
But you just said "people who share my ethnicity", which has nothing to do with race. People of any race can share your ethnicity. Is a black Mexican closer in culture to a Nigerian or to a Mexican?
I'm not sure you understand how governments work. That's ok. On a census, there's no box to check off every strain that makes up my ethnicity. There's a box that says "Hispanic". I'm being descriptive, not prescriptive.
You're right. My comment was uncharitable and US-centric. Sorry. I found it hard to not react because of the personal stake I feel I have in this sort of conversation. I'll try to do better.