I agree with you that he is offside. No question his foot is past the defender. But I don't agree that he broke the spirit of the law. The rule is in place to prevent an attacker from just parking themselves way downfield and that is obviously not what happened here.
I hate thinking of it like this, but we just have too much info. If we didn't have the computer simulation and could only rely on the video, no one would complain if the goal was allowed. Well OK, the Germans would complain, but no one would take them seriously. It's similar to baseball when a runner slides into second, clearly beats the tag, but as he's sliding his body comes off the bag for a split second while the tag is being applied, and he's called out. By the letter of the law, he is out. But in the spirit of the law, he should be safe since he reached the bag before the tag was applied. And with just real time video, no one would complain. But because we have HD super slo-mo video zoomed in on the bag, we can see his body barely left the bag when his armpit passed over and he's called out. It's stupid.