The German passenger, in the film, didn't just offer to negotiate--he stood up and shouted to the hijackers that something was happening. I know that this wasn't based on research because, in connection with research I've done for a project at work, I've read every record and transcript of every phone call made from the plane. Nobody said anything about any such thing happening. As for your statement that "Continental Europeans are more likely to take such a position", I don't know, that's a mighty big generalization, based on the actions of nations rather than individuals. The real crime here is the emotional brutality visited on Christian Adams' family by the filmmakers. Given the tiny bit we know from the phone calls, there is every chance that he was a hero right along with the others.
You are correct, he did shout to the hijackers. All that I can say is that if you haven't talked to Europeans lately about this subject, then I suggest that you do so. I lived in Germany for 4 years (some years ago), but my Stepson lives there now, and you simply would not believe what he tells me Germans say to him about this subject.
Also, the lack of a backbone on the part of the French leadership during recent Muslim riots and Spanish elections after the terror attack seem to show that many Europeans want to stick their heads in the sand and ignore the threat to their world.