The problem is that huge swathes of the populous world have very bad and corrupt leaders and dictators, who strip much of the wealth of these countries and keep it for themselves and their ‘iffy’ cronies. In doing so they help impoverish their countries, forcing those subject to their moral mismanagement to seek ‘greener pastures’ elsewhere - the US, Canada and Europe are seen by many as being those very pastures. The issue is that we can’t take them all in - there are potentially many many millions; and if some are let in, then why not all the others? Why should we favour some and not the others?
Of course the other issue over letting large numbers of migrants into ‘our’ countries, is that it impacts the economies, demographics, cultures and society - that these folks do not leave their psychological and perceptual issues, expectations and demands behind, they tend to bring them along for the ride. -A significant minority also bring criminality and even terrorism with them. When it comes to criminality, well, I for one feel ‘we’ already have more than enough ‘nere-do-wells’ residing within ‘our’ communities.
We live in increasingly morally and spiritually ‘interesting’ times.