Matthews was just rambling on MSNBC, and as someone said above, Matthews was postulating "Hispanic" might not be the correct term for a Cuban national. Given some recent national stories, where the meta-narrative from right thinking people is that a person is what they self-identify as, it's just funny our friend Chris would mumble this thought crime.
"Right-thinking"* people don't say that a person is what they self-identify as but that taxonomy are always constructed. Latino is a complicated one because it makes no sense to a Spanish person and would be totally weird in Europe but sorta wonkily works in America. One of the initial uses of these theories (way outside the race or whatever context) was just to show there were social conditions making thinking, saying and acting certain ways possible or unconceivable.
*by right thinking I'm assuming you are talking about the progressive side of the recently flared USA identity wars. These people aren't theoreticians but they are using theories that they might not understand and/or use properly.
As for the Matthews thing I have no idea what is going on but going from "only dems can be latinos" to "Cubans are not latinos" already seem a pretty big step so not sure what you were drving at (not saying you're full of shit I'm just confessing I don't get it.)