Context: response to the proposal of unlimited immigration.
No (D), this is a horrific idea, that would hurt workers the most, and dis-advantaged urban areas. We can see this happening in the UK and other countries. A nation with multicultural, and multi-ethnic vibrancy can only work in the confines of controlled immigration, immigration to deal with the country's needs, and immigrants that contribute to society
A nation-state is an important aspect, but I wouldn't expect white Europeans, who ruined that idea through imperialism and colonialism to understand.
I don't know why this is morally questionable.