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.
I'm not calling anyone anything. The GP of this post claims to be of Hispanic race. You claim he is not entitled to call himself that. Are you the the arbiter of what he is allowed to call him self? I'm must admit I do find it ironic when you simultaneously claim groups of people don't want to be named and then at the same time are trying to prevent somebody from such a group to call himself that.
It seems like you just want to be argumentative for the sake of it. If you review our comments, you'll find where you called it pretending and you'll not find where I said he couldn't call himself whatever he wants.
In the meantime, consider why many people don't want to be lumped in with people they have nothing in common with. If you take that thought seriously, you might learn to see the world somewhat differently.
Maybe I would learn something if you could actually provide some evidence besides being needlessly patronizing. Who are those people? What do their feelings have to do with a fact that there exist a set of traits which which could be used to subdivide us into groups?