I consider my son white but his fathers family doesn't

My son's father's late-father (rip) was 1/2 Argentinian born in Argentina (mother was white) I, myself am white. So not that I disregard my ex's genetics because obviously they're there, but when asked, my son is white. He's blonde hair hazel eyes. My ex's family thinks it's an insult that my son's legal forms and such classify him as white... 🤔 I classify him what a majority of his genetics are... if he was 1/2 White and half something else then I could understand but he's not. He's kind of a mutt like me but white... am I wrong? I only do it because that's legally how it works right? I'm not trying to be disrespectful or anything. They consider him Argentine/Argentinian but maybe it's because of the blood line? Because he's male? They said males have strong genes so he probably has more than females in his situation ... 😐 I choose not to argue and continue his legal forms as white out of respect and honesty. 
     EDIT: well I thought he had to be 1/2 but he's 1/8 (correct)? I'm confused I don't want to deny my son his and their heritage I was just going by what I was originally told by the staff at the hospital for his birth cert. his family wants him listed as Hispanic... this is why I'm confused sorry if I sound dumb but I was told to list him as white. Maybe I'll look into changing it to list both? His Grandpa on his dad's side (my son's dad's father) is 1/2 so that makes my son's dad 1/4 and my son 1/8.