I don't really see the ridiculousness in it. It is a fact that they where keeping Germany fighting which allowed the Nazi atrocities to keep on happening, which by the way a lot of German regulars took part in even in france. Its more indirect then the people literally gassing people and the people ordering the gassing but they are enabling the gassing to go on by keeping up their fight. I seriously don't see how that doesn't in the very least make them partially responsible for what was going on.
Query: Is every soldier who fought in the Red Army partially responsible for Stalinist atrocities? Y/N
Is every soldier who fought on the Communist side in China partially responsible for Maoist atrocities? Y/N
Is every soldier who served in the British army during the Empire partially responsible for assorted imperialist atrocities? Y/N
Is every soldier who fought in the American army partially responsible for atrocities against Native Americans and Filipinos, Jim Crow laws, and various 'missions' to Latin America? Y/N
In all these cases, soldiers aided and abetted their nations, even if it is just by cleaning latrines in a remote outpost, helping them to do not nice things. What's sauce for the goose is sauce for the gander.
And while the Nazis were worse than the above, I will not condemn someone as a horrible person for not committing treason, even against a horrific state. Since treason is arguably the most foul crime in the mind of man; the lowest circle of hell in Dante's Inferno is for traitors.
By that standard, the Allies in the 1930s are also partially responsible for Nazi crimes, as if they'd had a spine and brains Hitler never would have got going and caused so much damage.
To me, Rommel is the classic example of 'good man, bad cause'. That he earned respect from his foes during wartime speaks a great deal for his character.