No one can dispute his proposal to build a high wall (I heard 50 feet high) along the4 US-Mexican border, but I'm not sure how he's going to get Mexico to pay for it.
Particularly not after Mexico's president has disdained talking to him...likening him to Hitler. (I've heard that he intends to build it using Middle-Easterners as slave labor. )
Edit: "No one can dispute...." is a pretty broad statement; documentation would be in order.