Whenever you have to ask that question, it is often a better idea to sit down with a nice cup of tea, and take some time to reconsider what the person you are replying to was intending to do with their comment.
The comment pokes fun at people holding grudges for that long, on behalf of their ancestors, and at the whole situation in general. Ultimately is is meant to make people think whether demanding reparations from a less well-off people is really a better idea than just moving on. If everyone held grudges like that, no two people on earth would have good relations and we'd all sit in our little caves brooding over some slight our neighbor's ancestors inflicted on our family ten generations ago.
No, I'm not arguing for genocide. But thanks for the laugh.
They should've learned from the French making sure there's nobody left to hold a grudge.