Think on walls (Physical and symbolic) used to stop migration, list arguments in favor and against them.
When I think about walls, definitely I cannot only refer to the wall built in Mexico to avoid the migration of Mexicans to USA, but about other walls built in different times to separe countries or cultures and avoid the migration of ones (generally poorer) to the other regions that represented more opportunities for them.
If I made a list of them, they would be:
- Great wall in China
- Berlin wall
- Apartheid wall (Cisjordania wall)
- Frontier wall between Mexico and USA
Off course all of them have different connotations, according to the time and according to the purpose of them. What is common among them is that besides the avoidance of migration, they did not allow spread of culture to emerge. They just enclosed one region to avoid the invasion of groups of people with different behaviors, different ways of government and different interests... Also looking for different opportunities.
The word in the last paragraph is "different", and maybe that is the idea of builiding a wall to separe (can be physical or also a symbolic barrier): Fear. Fear of feeling invaded by other culture with differences, with ability to work more for less, fear of losing control over regions.
In general, establishing barriers in order for people not to enter to a country has many reasons: Cultural, economic, social, human... Cultural, the mentioned before. Economic, to prevent the increase of foreign labor taking the jobs supposed to nationals. Social, to avoid the inclusion of other cultures (avoiding inclusion leading exclusion) and Human, since we have a sense of territoriality and we protect the place we live in.
For me, there are no reasons to be in favour or against barriers for movement of people. Which is clear for me is that, when those barriers lead to exclusion and discrimination, equity cannot emerge, and is in this part when those barriers become a destructive weapon for societies.