I think the Nazis would raise indictments for crimes committed historically. Thus Churchill might be charged with causing the deaths of German civilians during the First World War by enforcing the naval blockade while head of the Admiralty. The Treaty of Versailles would no doubt be represented as an act of brigandage, and those who perpetrated it charged accordingly.
The Germans might claim to represent the interests of the colonial subjects of the British Empire. They certainly paid at least lip-service to the cause of Arab nationalism historically, and formed foreign Waffen SS divisions such as the Indian Legion. Presenting themselves as the champions of subject peoples, would be of great propaganda value both domestically and abroad.
Thus the Germans might accuse the British of waging imperial wars of aggression, e.g Afghanistan, Iraq, the Transavaal. Even the Zulu War was within living memory at this time. They might read damning testimonies to the courts of the conditions Boer civilians had to endure in the British concentration camps in South Africa in the Second Anglo-Boer war, i.e. starvation and typhus epidemics. The Belgians might be similarly arraigned for their brutality against the Congolese in their Empire. While the Germans were being damned for the sacking of Louvain, the Belgians were mutilating, flogging and murdering African forced-labourers in their rubber plantations.
The Germans might win advantage in the Arab World by making a public spectacle of such Anglo-French breaches of faith as their betrayal of the Sykes-Picot Agreement. Obviously they would make much of the Balfour Declaration also, given the anti-Semitism common to themselves and the Arab world.
