Are they so racist that they think that all Latinos are the same and automatically vote Democrat?

Yes, and it's quite funny too. When you get down to it there's all sorts of latin american migrants in the US. And the ones likely to vote Democrat probably won't get the right to do so.

I tried to make the point that the sort of person that has the money to migrate to the US in a way that they get to vote is likely a wealthy person whose only connection to the home country is exploiting its health care system. Not to mention that countries in Latin America are a) amongst the most religious conservative in the world; and b) becoming less catholic and more puritan because the pope is too woke for them. I was told I was racist against latinos.

I think there's also a counterpart to this as a bet that Republican's notion of whiteness can't expand to include 'mexicans and other latinos'. Which is only true in so far as it bars potentially democrat migrants from voting. Right wingers do not care that the right wing hates them on the grounds of race or culture. A gay man who's a right winger will keep voting Republican because they know they are protected by their wealth and/or class. Likewise for the white passing Latino that moves from 'Communist Homeland' to Miami. They voted for the 'Tropical Trump' before, and they'll vote for the real deal as soon as they are able.