If we are willing to act violently in pursuit of a peripheral interest, everyone can be certain that, when a vital interest is at stake, we will be still more violent. 'Credibility' is defined as the willingness to kill a lot of people now for a not very good cause to assure the world that we'll kill a lot more people if we can find a better one.
Six million jobs in the US depend on trade with Mexico. Ten border states - six in Mexico and four in the United States - combined have the third or fourth largest economy in the world. Twenty-nine US states depend on Mexico as their primary export market.
To act intelligently in human affairs is only possible if an attempt is made to understand the thoughts, motives, and apprehension of one's opponent so fully that one can see the world through their eyes.