Hispanic isnt a race?

Why do people fail to realize that hispanic isn't a race its an ethnicity.You can be a Black Hispanic (Zoe Salanda,Sammy Sosa) You can be a White Hispanic(Alexis Bedel),You can be a Mestizo Hispanic(George Lopez),You can be a Mulatto Hispanic(Vin diesel).Also why do some "hispanics" who are obviously black,claim they aren't because they speak spanish?Im baffled how some people who are darker than me or look like we can be related get offended when you call them black.