How can I be responsible for the decisions of other people that were made before there was even the smallest inkling of a concept of a person who would become me? It's pointless to guilt-trip myself over what my ancestors might or might not have done, because there is no way I could have possibly stopped things from going as they did or changed the situation. As others have said, so long as I act with decency towards one person as I would another, regardless of color or ethnicity, then I have no reason to take historic ills upon myself as if I personally was responsible. I have enough to deal with as is, thank you very much!
That being said, I do not think the world nor the human race is hopeless - if we had no purpose beyond eventual (self-)destruction, why did we start to exist, why do we continue to exist, at all? It would seem like a waste. Besides, if everyone took the view that it was all hopeless and destined for failure, then no one would try to be pleasant and make the world better - there would be no purpose in it, after all. Even if it does all go to crap some day, we should at least act as if we can't fail and set our sights to the highest. Setting one's sights on perfection will guarantee at least somewhat of a better turnout than settling for failure from the start. Resigning oneself to worldwide destruction more or less implicates one in the actual problem, after all. I'd rather choose hope, even if it turns out to eventually be wrong, than convince myself that my own existence is pointless and problematic.
And I do like gelato.