You on the other hand seem very certain that not one additional mile is warranted. I don't see how anyone make that claim.

Oh, I don’t reject the possibility that there might be a mile or two of fence here and there that might be better served by a wall. Just that the problems we face at the border aren’t ones that will be solved in any material way by doing that.

We’re already doing an excellent job of moving crossers to places where they can be detected and detained. Partially because of the fences and walls that have long been there, and partially because the crossers these days aren’t trying to evade detection very much. Our problem is that we don’t have adequate systems in place to handle them once we catch them. We don’t have enough detention facilities or immigration judges.

Building more walls doesn’t address that problem. Because most of the border can’t be blocked by a wall - ever - you can’t ever physically prevent people who are willing to cross and be caught. So you have to solve the problem of what to do with them after you catch them. That’s the main failure point of the system right now - not a failure to have enough wall.