This has nothing to do with skin color.
If you like a particular genre of music or tv, a style of food, or even a religion, I see no problem in creating threads for those things. It just seems wrong to setup an official thread for a race and start using a different language in it. Rather than sharing culture with others, you are intentionally excluding people from the discussion by having jokes at their expense in a language you think they can't understand (as with the T-shirt picture).
I've seen threads here about different countries, regions, and cultures before. We've had Muslim-GAF and Euro-GAF and that's fine because it's understood that different races of people can participate. However, "HispaniGaf" is about being Hispanic. It reinforces the point by putting a language not everyone knows right in the subject.
If this was a thread about GAFers in Mexico or Spain or Cuba, it would be different. Because anyone can live in those areas and doesn't have to be born Hispanic.
But that isn't the case. I look at this thread and it feels like a private club where people who aren't born into a certain race are outsiders. On a public discussion forum, that sends the wrong message, in my opinion.