What do delaney and Jardine argue about?

In Chapter Seven, Delaney runs into Jack Jardine, who comments on Delaney's passionate appearance at the town hall meeting the other night. The two get into a discussion about the gate. Delaney calls it "irresponsible," citing his belief in a democratic society, while Jardine cites safety concerns, going as far as saying that such safety measurements will be necessary until the borders can be controlled. Delaney is outraged at this statement, countering that the United States is a nation of immigrants. The two go back and forth, arguing the benefits and detriments of immigrants in the United States until Jack's son, Jack Jr., runs into them.