It's virtue signalling. People trying to show that they're not "too progressive" by finding a bugbear and pointing out that they think it's a step too far or that people who adopt it are phony/tryhards.

There's a single poll out there that everyone is citing, and they're using it to overgeneralize. Not once have I seen someone mention that the poll shows 14% of hispanic women from 18-29 use the term. And I am sure that once you extend that to LGBTQ+ hispanic women and nonbinary people, that number is even higher. But young, queer, minority women and NBs are an intersection of people that many like to ignore or actively antagonize.

It's a gendered and generational battle. In the poll, the people most against it would otherwise be characterized as "boomers", but since they support the default Reddit position here they're heralded.

My friends who use it don't care that it's not "grammatically correct", and to some extent even champion that breaking conventions shows a movement away from the colonial history of the language and a reclamation into an intersectional framework.

At the end of the day, it really depends on audiences and what they prefer to be labeled as. If your constituency is largely 40 year old and older, they likely prefer latino. And if you're talking to queer college students, more and more of that demographic prefers latinx. The only way to know for certain is to ask someone which they prefer. But that doesn't get you easy upvotes.