I saw last night the peso dropped one half.
One half of what? Its own miserable value?
....I saw last night the peso dropped one half....
That just means that the wall will cost Mexico twice as many Pesos. No big deal.
Actually, yesterday The Mexican peso dropped from 18.5944 pesos per dollar to 18.3226 - a drop of about 1.5%. Today it's trading at 19.7537 pesos per dollar which is very near it's year-to date-high.
Truth is, massive drug dealing and emigration have a negative impact on the Mexican economy, except for the drug cartels. And while NAFTA has been great for their balance of trade most of the profits go to giant foreign owned (mostly US) companies. Average Mexicans don't see any benefits. If Trump scraps NAFTA and the wall gives the Mexican goverment the upper hand over the cartels, his policies could very well end up benefiting the Mexican economy.
Trumps reforms are humiliating to individual Mexicans since the wall, from their perspective, says "you're not good enough to come to our country." The reforms also interfere with the reconquista of the American Southwest (see any good Mexican elementary school history text.) It's not really the economic impact that has people riled up.