I do feel bad when I see discrimination, but discrimination is not limited to ethnicity or race. Even if you look at strictly at racial discrimination, it goes in all directions, including people of African descent who judge each other on the lightness or darkness of their skin.
And slavery has been around since before recorded history. Native Americans (especially those from Alaska and Canada) regularly enslaved the tribes they conquered. Some of the first Irish settlers in America were sent here as slaves, as well.
As for the need to apologize, I'd be more inclined to apologize to the people who actually were/are slaves (check out the current situations in Africa regarding the following industries: gold, diamonds and chocolate). I rarely agree with the views of my parents or brother, so I can't understand why I'm expected to answer for people two hundred years ago, that I never even met! (I had ancestors from both sides of the issue.)
Here's a question that troubles me: my grandmother was born without the right to vote. Women were "chattel" or "property" of their fathers or husbands. Does that mean I expect every man in the world to apologize for how my foremothers were treated? No, I don't hold you responsible.
My response to the sad history of slavery and other discrimination is GRATITUDE for ALL the people, of every color and gender, who took a stand and said "This is WRONG." There were consequences for all of them to be outspoken or to help an escaped slave, but they did what was right. I want to express my gratitude by telling the stories of people who do the right thing regardless of the cost.