This is a fascinating statement because it tells us something of the nature of Mormon’s vision of the future. While he may have seen the events of the last days, he did not see clearly enough to understand the cultural and social changes that would occur between the time the record was hidden up and when it was to come forth. Mormon is picturing the descendants of the “remnant of this people” in the same context as those who have conquered them, and who are setting the tone for the world as it will be in the future as far as Mormon sees it.
This suggests to us that Mormon saw the future as one where the Lamanites that he knew were still the dominant culture of the remnant of his people. Mormon did not clearly foresee our day in terms of culture, but rather saw the future in terms of what he could readily predict. This is the reason that he specifically mentions taking up arms. The Lamanites who have attacked the Nephites are the wave of a future in Mesoamerica that was bringing increased warfare. Mormon had seen the fruits of it, and condemned them. He is speaking to these Lamanite/Gadiantons that he sees as the future, and telling them that they must cease the killing. They did not listen. Sadly, mankind has not listened.