I would not make any excuse for the abuser.
Extreme intoxication can lead some individuals to ignore (drop their guard), or fail to realize completely, what is going on. How many drunken sailors have awakened the next morning in a bed that they have no idea how they arrrived at and with a girl who they do not even remember meeting?
To take advantage of someone who is very intoxicated, particularly if you helped them get intoxicated, is no excuse for your belief that they were "willing" at the time.
If the only thing that is known is that they were drunk, you weren't and they regret what happened, then the onus must be on you that they were taken advantage of. You could have just pulled a blanket over them and let them alone.
It happened to me when I was 16 or 17, so I know what you mean. I should be more understanding, but the military will not be. I also had a man try it when I was 14 -- took me home and tried to ply me with beer. When I realized what he was doing I ran out of the house at 3:30 in the morning and walked home, like 5 miles. What a frickin' drag that was. Next night at work, dude acted like nothin' had happened.