Vengeance rape: additional thoughts

As I understand it, there exists a type of justifiable action defense, meaning that what one does can be justified on the basis of security, fear, what have you.

But, for that defense to have validity, the defendant must be able to show that the evidence to support it existed, and was known by him, prior to his having committed the action he's on trial for, as well as show that his action was reasonable among and compared to however many possible choices he had. There's probably more to it, assuming I'm even remotely close, but what bothers me is how it seems his supporters will put themselves in his position, and try to act as if they are in the same circumstances as him, when a majority of them could not have his knowledge of the crime which his criminal act was an apparent vengeful response to. He is largely being excused by information known after the fact, information that a humane person would see as irrelevant if they were watching the second alleged rape happening, and they would ask for proof of crime and guilt thereof for the first crime.