Morality of Immigration/Borders
Yes indeed it is a difficult situation (to think about), especially for anyone who has empathy for others. There are masses of people wanting to migrate for a host of reasons ranging from life threatening persecution and poverty to seeking Shangri La and everything in between. The age of communication has increased the appetite for migration and also enabled a variety of methods of migration, such as trafficking and now the walking train of Guatemala. On the other hand, the age of communication has done little to increase empathy for migrants - dead toddlers washed up on the beach doesn't cut it with most of the prosperous populations of the target nations, where the age of communications has seen a huge rise in hostility to "others" and defensiveness against a perceived invasive threat.
On the other hand, I really do think that there are far too many impoverished people from poorer regions of the world wishing to seek a better life in richer nations for uncontrolled migration to be allowed. It is unsustainable and would lead to chaos. And yes resentment from large sections of the host populations when change happens too fast and on too large a scale. This might be an unpleasant realisation, but it is a fact that will not change. And while extra provision has to be made for people fleeing from opression and danger, it is clear the asylum system is being sorely tested by economic migrants.
So what to do? Firstly, I think we ought to recognise that countries targeted for migration have something in common. They are generally speaking "liberal democracies". People want to move to liberal democracies, ideally. They like what they see. In the long term the current batch of liberal democracies need to "export" their political system to the world and not do the opposite for selfish reasons - e.g arms sales and trade that enhances the elites of despotic states who are never going to allow trade to soften them like what eventually happened in the west throughout the course of the industrial revolution and in to the twentieth century. This exporting of liberal democracy should not be seen as patronising or colonialism - it is a vital mission, and one that should not be driven by material benefit for the exporters.
In the shorter term -but linking in with the idea of the liberal democracies jointly selling their philosophy to the rest of the world - they need to pick out countries for privileged treatment that are going to respond best to massive aid and then accept migrants as citizens. The developed world can still have its quotas for migration.