Why anyone would want to live in a completely homogeneous sociery is beyond me. Diversity is good. Helping people who are in desperate need is right and feels good.
Is this just a figure of speech or are you literally unable to understand the reason? Diversity doesn't just pop into existence. It's the result of a process.
"Diversity is good" is a meaningless, dogmatic mantra to most people in the world. "Diversity" is, as can be plainly seen by reading the news, often a cause for conflict, transitional pains and erosion of social trust. Most people want to be surrounded by people that superficially look like them and belong to the same "group", and the arrival of anyone from an "outgroup" (who isn't a tourist or trader) causes distress to them. They can be taught/raised to feel different but most people who grew up in relatively homogenous societies never had to do that by the time it's too late.
Not only are there people like that, but also those who don't have a problem with "others" per se but have seen what happens when "others" increase in numbers. The aforementioned people are going to be afraid, angry, and then vote right wing governments into power which means life gets worse for EVERYONE who isn't rich.
Sure it would be great if this deeply rooted aspect of humanity which fuels bigotry and racism worldwide did not exist and everyone could get along fine, but let's go back to reality for a second.