Puhleeeze
That is NOT what the author suggests or I consider, a valid assumption.
No, what is hinted at herein, is the possibility that Mexico would/could very easily find other "buyers" for their precious oil.
Is that scenario so far fetched as to stretch the credulity/credibility in your mind?
So Mexico sells to someone else and we buy the oil the other buyer would have bought. Oil is oil. It is a fungible commodity.
You may be correct, but I do not think that we should sell our country/culture down the river by allowing illegals in exchange for oil.