Virtually all of these are spurious in the extreme but the argument with the most scary logic is the one which suggests that 'rich Western nations are helping the people in Third World countries.'
NOTHING could be further from the truth! You do not help neighbours by inviting countless people to come and live in overcrowded conditions in your own house!
There are rather too many people in absolute poverty across the globe for such a thing to work and even if it did, it is merely 'a sticking plaster over a gaping wound' kind of solution.
Who are these immigrants anyway? - The younger and healthier who are desperately needed in their own nations? The better qualified from these nations perhaps, which then robs that poor country of again, what it so desperately needs?
Consider Malawi where doctors and nurses flee to the West for a better lifestyle leaving that nation almost entirely without!
No. Such peoples must be helped in situ. They must receive aid and be encouraged by the world to weed out corruption, despair, lack of opportunity. They must be supported financially and with special trading arrangements. Their infrastructures should be constructed for them. Tyrants must be deposed by the UN.Their most talented and fit to come to the West and leave the problems fully in place? - NO WAY!