There is a problem with that. Who are the "they" in that statement. If 99% of Latin America got together and agreed they hate Latinx, does that mean the remaining 6 million that prefer Latinx have to shut their mouths and accept it?

No group of people are monolithic. Like how some Native Americans prefer "First People" or "American Indian" and some legitimately want you to actually say the name of their tribe or nation when you refer to them (because lumping "them" together into a single unit is itself a label applied from the outside and not necessarily a group they identify with). My experience with people is that Puerto Ricans prefer to be called Puerto Ricans and Columbians prefer to be called Columbians, etc. The only time you need to talk about Hispanics or Latino/a/x/whatever is in abstract demographic conversations or maybe something like influences on a genre of music.

Personally, I don't give a shit. I'll try to be respectful however I can and if you ask me to say something different, I will beg your pardon and say what you want me to say. Because (and I cannot stress this enough) I don't give a shit what is "the one correct answer", because there isn't one. I just use whatever makes the person I'm talking to feel respected and heard, because that's what actually matters.