I think the idea behind the apology is that it acknowledges that crimes were committed. People were unjustly screwed (and killed, etc.). And just because it happened in the past doesn't mean that it isn't still affecting the present. In fact, the nature of cause and effect kind of mandates that it does.

I think it's a good sign for the human race when conquerors get around to apologizing to the conquered. I think it shows that people are getting sick of conquering each other. We know that conquering is wrong. We're over the conquering.