Correction: I am the real Dave.
The Border Wall - should it ever be completed - will be a DETERRENT for certain types of illegal entry. Keep in mind that at some point in the future, hopefully the DISTANT future - the thirty or so million illegals in the U.S. will be legalized, thus inducing ANOTHER flood of wretched masses to our borders, just like last time. Only this next time we will be a little better prepared.
Incidentally, the Border Wall will be a symbol to all of the wretched masses that we will, going forward, take our own immigration laws seriously.
And it will create some jobs, just as any large "infrastructure" project creates jobs.
What I would love would be if the Donald suspended enforcement of Davis Bacon, so that low-paid illegals could work on building the Wall.