I have had a few passionate discussions with people over the last few days on migration. People have always been migrants. Border passport requirements are a post World War I innovation. The idea of National Borders preventing migration is indistinguishable from Apartheid. By definition. Apartheid means separateness, and is the idea that people are essentially different and we should primarily look after our own. Apartheid is the idea that it is okay to have laws that separate people based on factors such as race, place of birth, gender or whatever you choose to identify people by.
One of the primary objections to migration is that immigrants 'steal jobs'. That there are a set number of jobs, and if someone enters the economy, they take a job. That is wrong if the person is a positive contributor to society. Every person entering eats, sleeps, gets haircuts, meets up with friends etc. Each person entering grows the economy. Job stealing sounds like common sense. It feels logical and resonates with our in built desire to look out for our own first. It's just wrong if you look at the evidence. Even if other people are suffering, we need to look out for those around us first. Others can sort out their own problems. It is fine if you believe that. Just own it. It's called Apartheid.
Ironically, the lower paid jobs are mobile without immigration. Businesses move factories. They move where they do things. I had a friend who was told recently his job was moving from Cape Town to Johannesburg. He chose not to follow it. Lots of manufacturing jobs have moved east and masses of people have been lifted out of poverty. It is one of the most remarkable features of the last 20 decades. Closed borders benefit the rich more than the poor. They stop the IT executive professional in India moving to America, but they don't stop the call centres being outsourced.
World Economic History - Max Roser
The most comprehensive review of the issues surrounding borders I have found is on the Stanford Encyclopaedia of Philosophy. There are a lot of big global issues that I have no clue how we are going to fix. People are incredibly creative, resourceful problem solvers when they are allowed to be. We don't need to solve big problems if we empower people to tweak small problems. At the very least, don't stop them from trying because they are different.
There is a path to a better way of doing things. One step is to welcome people who accept the constitutional rule of law, and are looking to be contributory citizens.