Apparently the theory is that he gave up this family to save his own family, which is a horrific situation to be in. So even if we knew this is what actually happened, and we don't, it's an obvious mitigating circumstance.
No, but it adds insult to injury. Keep in mind that the Germans used all kinds of pressure including the deportation or execution of family members to get people to betray others.
There were extensive legal proceedings post WWII here, the only way people got away with stuff like that is if they fled abroad, even well into the 80's collaborators and other people that betrayed the local population were discovered and tried and convicted.
But this sort of 'posthumous trial by media' is revolting in its own right, especially because the instigators are simply trying to make a buck off the back of Anne Frank (they're not the first and likely won't be the last).
Apparently the theory is that he gave up this family to save his own family, which is a horrific situation to be in. So even if we knew this is what actually happened, and we don't, it's an obvious mitigating circumstance.