Hence the wall.
Countries have the right, and the duty, to control who they let in. I have never stated otherwise, and I don't recall any others stating it either, although people have been vilified as if they had. This is what is basically normal now in online discussions, I find. Hyperbolic misrepresentations of what others say, when they disagree with you, is now par for the course.
It is the very essence of tribal-based "debate".
Today's Dilbert cartoon (
http://dilbert.com/strip/2018-07-08) illustrates this well.
My own gut feeling is that the wall, assuming it's actually ever built, will be about as successful as the "war on drugs". I would have thought that conservatives would want to be more careful with large expenditures of tax monies of this nature, but sometimes it seems as if the security industry is immune from scrutiny. I'm not saying that the wall would not be partly effective, I'm sure it will stop the low-hanging fruit very well. Even the war on drugs made many street-level arrests. If that's ok with you, well, it's your money. I'm just saying that a little more thought might yield better results, assuming you want results and not theatre.
This all depends on your point of view of course. The security industry probably thinks that the war on drugs is fantastic as it allows them to feed at the public trough to their heart's content. I imagine that brick and concrete lobbiests and contractors are wetting themselves at the prospect of a long wall.
Trump's "muslim ban" is an interesting case in point. If I understand it properly (and I'm not certain that I do, it has undergone some changes and I don't follow them daily), it really only explicitly restricts entry from some countries and not members of a specific religion. But according to the Wiki entry on the subject, Saudi Arabia is not on that list. That's kind of an interesting omission, given where the 9/11 terrorists came from.