Got their crunch time faces on?
There has to be a wall, and how can the wall, at this point in time, be built without military level security?
Construction crews would be sitting ducks for sabotage by anti-wall forces in the US as well as cartel interests in MX. One major incident and the news cycles and far left screechers will run with it 24/7 with lawsuits up the wahoo, as well.
With congress throwing up roadblocks every step of the way and refusing to address laws that exacerbate the border problems you're going to have to consider some type of martial law scenario or declaration of war to take the detractors out of the picture. How else other than DECLAS to show enemy interests the of detractors with the institution military tribunals to replace a exposed corrupt justice system? All other options have been exhausted IMO.