What we have here is a difference of historical interpretation as to Reagan's motives. That's ok. You posit that Reagan got tricked by the Democrats, I'm more inclined to think it was part of lowering labor expenses for the benefit of businesses large and small, and to bring down unions (chamber of commerce type stuff).
A third possibility is something Reagan alluded to in the above-copied tv debate with GHW Bush. In the context of the Cold War, there was real concern that Mexico might become another Cuba. Therefore we needed to relieve a lot of their surplus unemployed (Reagan mentioned some 40% or so unemployment rate in Mexico) else risk a Castro-style leftist revolution next door.
I wouldn't dismiss this third possibility out of hand, as so much of what we did in the Cold War (from underwriting the defense of Europe to supporting Apartheid South Africa) was done for the overarching goal of preventing communist/socialist expansion.
[On edit] - I re-posted the Reagan vs. GHW Bush 1980 debate below. GHW Bush displays the "compassionate conservative", while Reagan apparently steps back and views immigration through a Cold War lens. Reagan seems to be saying that we needed to let in many, many more immigrants from Mexico to relieve their massive excess unemployment--40-50%--lest we find ourselves with a very hostile and strange (i.e. leftist, Marxist, Castro-like) neighbor next door. Reagan even references Castro's Cuba in this answer/speech. If you take Reagan at face value here, the Cold War trumped all other considerations regarding immigration.
Last edited: Apr 18, 2019