It's not, but then facts have never been your strong suit on this issue.
It makes no sense to you to close the border on which over 50% of illegal immigration occurs, simply by walking across on dry land, because "that would leave the back door open."
Okay ace, what is the good of declaring a war on terrorism then leaving every door open?
If your goal is to actually secure the country against terrorist threats, as you now claim...yeah, it makes no sense to not secure ALL of the borders.
If you're just trying to stop illegal immigration from Mexico, then you're saying that stopping terrorists is not an especially high priority.
Which one is it?
"...what is the good of declaring a war on terrorism then leaving every door open?"
EGGS--ACTLY!!!!