But it is a bit dogmatic.
If you have a neighboring country that is extremely poor next door to a wealth country then there is likely to me massive immigration even without welfare being offered.
Along with this will be adverse social changes (okay there will be some benefits too) where the people immigrating want to live as they did in their home country which will be a threat to the local culture (sorry but this is a normal human reaction).
I am more for allowing people in other countries access to trade so that they can build wealth within their own borders. I do think that multiculturalism's main benefit is to reduce the conflict between peoples as we all know someone from another background and can see that generally all peoples are good but any change should not be to sudden and should also be able to be resisted by the existing peoples.
If immigration controls were totally relaxed then massive immigration would be a fact of life. This would cause social chaos in the host country and could result in a civil war as people are threatened by the other group.
Would it be okay if 10 million people from another country to move into a country overnight?
This would be a passive invasion and would be being so altruistic to open up your country to be taken by another group without firing a shot. In this context it is insane.
Lord Acton, Lord Chief Justice of England, 1875 - "The issue which has swept down the centuries and which will have to be fought sooner or later is the People v. The Banks."