What was Operation Wetback? Explain why Mexicans had conflicted feelings about it? Why is this being discussed now? http://www.npr.org/sections/thetwo-way/2015/11/11/455613993/it-came-up-in-the-debate-here-are-3-things-to-know-about-operation-wetback

Operation Wetback was a program implemented in 1954 in the United States, with the help of the Mexican government, to deport undocumented immigrants. Approximately a million immigrants were rounded up and deported within a few months.
The history of this actually dates back to the Bracero Program of 1942 which facilitated migrant manual laborers from Mexico finding employment in the United States. Along with documented workers also came undocumented ones who because of their lack of legal status were subject to extremely low wages and bad working conditions. Many of the Mexican immigrants who were in the United States legally and the Mexican government initially supported or at least were partially favorable to Operation Wetback as a way of improving the life of documented workers.
The motives behind Operation Wetback were fueled by nativism and racial prejudice. The actual implementation was inhumane, with many of the deported laborers suffering or even dying in transit and families being spit apart and uprooted. 
The reason it is relevant now is that Donald Trump and the Republican party are advocating similar measures.