By this logic millions of German citizens who knew exactly what was going on and willfully ignored it should have been arrested and prosecuted. Not thousands, millions.
Same logic would say every North Korean police officer, soldier, or anyone working for the state should be arrested and prosecuted once that government falls.
Was this guy even a Nazi? Millions of Germans never joined the party. This guy managed to get into the SS and sat in a guard tower. He was part of something monstrous and horrible, but prosecuting a 92 year old for watchtower duty 75 years after the fact seems a bit excessive.
The one thing that gives me pause is his explanation of how he got into the SS. It strikes me as odd that a teenager with a heart problem managed to get in to the SS, even for concentration camp duty (and presumably not a real Waffen SS unit). With a heart problem he would have been far more suited doing civil defense stuff. So perhaps he is lying and the prosecutors know it.
If the guy was involved in war crimes, his age or the time since he committed the crimes should make no difference. Why should he be given a reprieve just because he had escaped detection for so long? Those who committed serious war crimes should never rest easy.
The one thing that gives me pause is his explanation of how he got into the SS. It strikes me as odd that a teenager with a heart problem managed to get in to the SS, even for concentration camp duty (and presumably not a real Waffen SS unit).
I might be making your argument for you but I don't have trouble believing that. Near the end of the war, the Nazis were so desperate for soldiers that they were pressing teenagers and middle-aged men into service.