Revisionists and Deniers are not exactly the same, but that is for another time. In Germany it is not permitted to speak of this at all, which is a problem. One theory that could apply to your question is that if someone else's crime can be made to seem so horrific that your own crimes can be justified by it, then pump up the allegations to the maximum. You have to make the opposition look like monsters in order to cover the monstrosities that you have committed (or are planning to commit). It still goes on today. Look at the campaign against Saddam Hussien, and now Bashir al-Assad. People only consider something a war crime when it is the other side that it supposedly committing it. If their side is responsible, it isn't seen as a crime. Sad, but true. As far as I am concerned, no one has to be killed for a war crime to have been committed. Just dropping bombs on facilities or installations in another country is a war crime.