Yes, 80% is considered a bit extreme. We have cultural clustering in the US but you won't find people advocating for it or describing this scenario as ideal. The initial poster was asking why he was getting downvoted.

An example of how this plays out is demonstrated in the article itself. The author says '80% asian-american' rather than 'asian neighborhood.'

From a political correctness perspective, people in the US don't want to be seen perpetuating anything that could be considered a form of segregation. Simultaneously it is considered negative to be seen as 'gentrifying' a neighborhood, i.e. disrupting the traditional demographics of a neighborhood.