The point is that H1B is marketed as selective immigration of highly skilled immigrants, but in practice it enables mass migration. Whether you think mass migration is a good thing is a different, and irrelevant, point. If you put "our immigration policy should enable the formation of places like Little Bangladesh" it would lose handily at the ballot box.
(By the way, Bangladeshi Americans are poorer than the average American: "In a 2013, NPR discussion with a member of the Economic Policy Institute and co-author of the book The Myth of the Model Minority Rosalind Chou who is also a professor of sociology. One of them stated that 'When you break it down by specific ethnic groups, the Hmong, the Bangladeshi, they have poverty rates that rival the African-American poverty rate.'" https://en.wikipedia.org/wiki/Bangladeshi_Americans)
> By the way, Bangladeshi Americans are poorer than the average American
The Wikipedia article is inaccurate. It claims that Bangladesh-Americans have a median household income of ~$59k. The actual sources cited by the article both say it's $78k:
(By the way, Bangladeshi Americans are poorer than the average American: "In a 2013, NPR discussion with a member of the Economic Policy Institute and co-author of the book The Myth of the Model Minority Rosalind Chou who is also a professor of sociology. One of them stated that 'When you break it down by specific ethnic groups, the Hmong, the Bangladeshi, they have poverty rates that rival the African-American poverty rate.'" https://en.wikipedia.org/wiki/Bangladeshi_Americans)