I've made this mistake myself, so I don't absolve myself, but this is a timely and well-needed reminder by Alisa Valdes-Rodriguez not to automatically separate Black and Latino. When we ponder uncritically about whether Latinos will vote for a Black President, we forget that many Latinos are Black. Most members of the "African diaspora", as the author puts it, live south of the United States. The largest immigrant group in New York City is the Dominicans, the vast majority of whom are Black. Many things we associate with Latino culture, from Salsa dancing to "La Bamba", have their roots in Afro-Caribbean culture, and prior to that, Africa.
There probably is some tension between non-Black Latinos and non-Latino Blacks. And that's worth exploring. But Latinos and Blacks are not mutually exclusive categories. And insofar as I've forgotten that, I apologize.