Holy Non sequitur, Batman.
Best I can figure, you’re genuinely confused. So here it is: no, Mexican isn’t a race. I know that. Congratulations! Neither is “Kenyan,” but if someone drew a picture of Obama’s Kenyan grandfather with a bone through his nose and a pot full of missionaries, I’d call it racist. And neither is “Chinese,” but if someone writes about a Chinese restaurant serving stray dogs, I’ll recognize it as racist.
“Latino” may not match any specific racial category, but since race is a social construct anyway, and since many people treat Latinos as a racial category distinct from “white,” I can recognize that posts like watchwolf’s are racist posts.
This is not rocket science, and trying to pedantic your way out of recognizing the bleedin’ obvious is not a good look for you.