For starters, it isn't my culture, since I'm not Native. I care about racism toward others because it's the morally correct thing to do.
I'd say roughly 100% of the Natives I know would say their ancestors' deaths still matter today. Who are you to say differently?
Indeed, Natives are dying today, before their alloted lifespan, because of the broken treaties of the past. Because of the poverty, crime, and disease caused by generations of trauma.
Do you celebrate Cinco de Mayo, Memorial Day, or the Fourth of July? I'd say those long-dead people--immigrants, soldiers, Founding Fathers--are just about irrelevant in 2012. Why are you wasting time on them?
You haven't forgotten your history, so why do you expect Natives to forget theirs? You're wallowing in the past just like you think they're doing. When you stop it, we can talk about Natives stopping it too.
And who cares what Del Rey meant? As I've written many times, it's the results that matter, not the intent. Her actions harm people whether she intended it or not.
If she's ignorant, then that's the problem--not my alleged sensitivity. Are you really in favor of ignorance? If you're not, stop apologizing for her and start criticizing her.
Would you accept her performance if she dressed up in blackface and an Afro wig? No? Then why do you accept this? It's the same thing, bright boy: portraying a minority using grotesque stereotypes.
I could go on, but I trust you get the point. For more on the subject, see 1491s on Redface and Blackface and Paul Frank's Racist Powwow.