D-Pirates---a wall, like any security measure or law is a deterrent, I can't possibly put it any more plainly. People should be deterred from breaking laws if laws are to mean anything.
A wall, a barrier a fence whatever. Trump quote?
A wall is what rich want to keep out poor. So the divide between rich and poor is a wall of deterrence.
1% rich is fine, as long it is not using most of Earths finite resources for that which is not necessary for sufficient standard of living.
How many years into the future the do the haves really believe humanity can go forward with an ever growing divide between rich and poor?
Ecologically environmental crisis---Erratic Climate Change--- will bring this to resolution;
1} one way{ die off of sustatainable ecological environment } or another,
2} human revolt against unfair and idiotic systems { brain//butt forward } that are not wholistically inclusive{mind//intellect forward }.