A thought provoking story. I have long wondered why the F & S words are used disparagingly since they are a source of pleasure. In the context of rape (happens to you when you don't want it) I can see how it applies to the usage you wrote about.
With respect to the military, part of the boot camp and basic infantry training is to condition people to willingly kill. Part of that is an obsession with correct terminology. If you use the word clip and you aren't talking about an M1 Garand rifle I'll most likely correct you with the word magazine. I always saw the "This is my rifle..." chant as a disassociation of killing and sex with an overt "it's your rifle, not a damned gun." http://www.usmcpress.com/heritage/marine_corps_rifleman's_creed.htm
The cadence chants often did have sexual words that had nothing to do with the indoctrination about killing. They were often nonsensical. A memorable one that one of my DIs liked was, "I don't know but I've been told. Eskimo pussy's mighty cold." WTH? While dehumanization of Asians was a thing for those of us on our way to Vietnam, why Eskimos?
The bottom line is that the context of the usage that you gave is about something unwanted rather than something we all enjoy. As you know, rape culture is something I didn't give much thought to since I see rape as an aberration rather than a norm. Maybe subconsciously why I like "cowgirl" where both parties are doing the doing. I hadn't thought about that until this moment.