Anyone offended by history needs to reflect on their priorities and identity.
I'm not offended that white people claimed this land at the point of a sword, and even worse, in the embrace of a smallpox blanket. Horrified, yes, but not offended. I'm not offended that the backbone of the economy for a hundred years was built on the backs of stolen people on stolen land.
I'm not offended by history.
What I am offended by is the present. I'm offended that people who have been oppressed and started out life with less than nothing have been told by the privileged elite to "pull themselves up by their own bootstraps like the rest of us did". That's fucking vile. I'm offended that we keep trying to whitewash confederate slave owning generals, instead of teaching who they really were, and what they really killed for, and ordered other people to die for. Be offended about what we are doing now, and use history as the reason why we should change it.