Coming quickly back to this, as I keep reading similar assertions. Testosterone increases urgency. It's a quality of libido, not the whole thing but a very important one nonetheless. I have some experience of this - nowhere near Seethlaw's - related to my PCOS and experimental treatment with spironolactone. My T was high for a woman and right at the bottom of the male range. Suppression made a strong qualitative difference to both my sex drive and my demeanour.
If you've spent plenty of time around men in a range of contexts, testosterone-associated urgency shouldn't be a surprise. In medical literature, the hormone promotes impulsiveness and competitiveness as well as 'virility'. It doesn't, in itself, promote violence or rape but those are consequences of disinhibited impulsiveness, competitiveness and sexual imperative.
Also, violence promotes testosterone production. Hard workouts do, too, probably because they engage the same physical processes as fighting.
I realise you said SA is nearly always about power and control, and rarely just sexual gratification. I think it's worth getting our heads around the understanding that testosterone drives a feedback loop involving both sex and aggression. Forced copulation can't be about violence alone, since a male body provides many more effective weapons than a penis.
As a sort of aside, the words for 'penis' in ancient languages were related or identical to 'weapon' (the word penis derives from this). I think this tells us something useful about how men feel when experiencing sexual urges.
'Crowd fever' demonstrably reduces inhibitions - it's why we enjoy big concerts, carnivals, sports events, etc - and its little brother, 'team spirit' can be very potent as well. I do understand how phenomena like tag rape and military sexual violence occur. You need to throw in some misogyny and dehumanisation as well, at least while getting the atrocity started.