I guarantee you those on the front line in Iraq and Afghanistan don't cherish the thought that while they are bleeding and dying in a rat hole on the other side of the planet their home country is being overrun by an unarmed invasion.
*See my past posts which use words like "tall concrete wall" "razor wire" "charge Mexico for our expenses" etc. and so on.
And our fighting men don't have to explain anything to anyone about their reasons for walking the line.