You should feel responsible. You should be willing to learn something. I certainly do.
Even so. If your Grandfather killed someone before you even were born. How could you feel responsible? It's not like you were able to whisper: "kill him! Kill him!"
But of course we can learn from that tragedy. Everyone can. But learning something and being responsible are two completely different things. It's ok if you say Germany's responsible though.
NB.: I'm of Jewish ancestry and have counted several Holocaust survivors among my friends. This shit is personal for me.