Thanks! for reading & taking the post seriously.
Here’s what I want to say in response:
Your “contradiction” is a false dilemma.
“Walls” (in inverted commas in the original post) are exclusionary walls.
Not all walls are exclusionary walls — e.g., Robert Frost’s mending wall.
The Wall of Humanity is a mending wall in Frost’s sense: a heartfelt protest against all exclusionary walls.