>>3700694 (PB)
If Ted Kennedy said "stand down" in the 1980's it would be unusual, unlikely if not impossible. As it was in quotation marks one assumes it's an actual quote, not a paraphrase or a reconstruction.
Therefore:
Most uses of “stand down” I’ve found in print are in the military sense, but it is used occasionally in the sense of “to back off” or “to stop an aggressive action” (“Medical marijuana protesters urge feds to stand down,” 10/11). Here in the US, “stand down” seems to be commonly used as a name of community programs and public-awareness campaigns designed to help military veterans facing endemic unemployment and homelessness (“Stand Down gives veterans chance to get help, give back,” 10/13/11).
http://www.word-detective.com/2012/06/stand-down/