> and other Heideggerian ideas, which have nothing to do with Nazism
That's begging the question.
We want to examine his writings to figure out a) how important is the biographical question to his work and b) how bad were the Nazis and why? Maybe thinking in terms of "Dasein" leads inevitably to death camps. Maybe not. But you can't just assume there's no connection (or that there is one). You have to argue it out.