The response of the Amalekite shows the difference in the doctrines between the two groups, and does so in ways that are familiar to modern readers. First step is the denial of an important doctrine. The second step is to deny that there is any evidence for that doctrine, and the third is to impugn the tradition that would lead one to believe that way. Note that the Amalekite says that these are “thy fathers and also …our fathers.”
In this particular response, the Amalekite is not only dismissing the belief in the Atoning Messiah, but also in the principle of revelation. He notes that the “fathers…did [not] know concerning the things which they spake, of that which is to come.”