We don't need the Nazis to destroy us. We are destroying ourselves, what does he mean by this

This is from the Diary of Anne Frank. Mr. Frank is the one who says this line. The Jews in hiding have been fighting over food. Because of the German forces raiding farms and taking most of the food for the soldiers, there is very little food to around. It's even harder for those in hiding to get food. Mr. Frank sees the fighting over the food as a way the Jews are destroying themselves. They cannot be divisive if they want to survive. If they are at war with each other inside of their hideaway, they'll eventually destroy themselves, the Nazis won't get the chance.