Nobody in this thread is objecting to self-description as latinx. We are objecting to the academic labeling of "a mixed gender group of people", or more accurately, the further labeling of the entire wide variety of people that fall under the already touchy "Latino" label. The problem is that latinx is a term to describe us.
You know why people keep calling it a white term? It's because the vast majority of the people using "Latinx" are anglo; the Latino communities you talk about where it's common are an extreme minority (See the poll this thread is about). Do you understand why it might be a bit offputting to have pressure to adopt a self-label from a audience of primarily white academics? You can't just say "Well it's not just white people" when they're by far the primary face of the word to the communities you're asking to accept it.
