why is it important to know the history of racism?

It's important to know where someone is coming from as another race. I wouldn't say to start full on studying every race's history ever, but a good thing is to read the news and maybe catch up on the brief history of racism. If you are white (as am I) it is hard if not impossible to understand where someone who has experienced racism is coming from. So it's good to know what not to do, and why, just to know.

So that history doesn't repeat.

to learn from mistakes

Trump's convinced many to reject info

Learning just how destructive racism is and the truly evil behaviour it leads to help us to avoid the mistakes of the past. Ask any Jew, Armenian, Copt or Cherokee.

So you'd remember not to vote for cross-burning Democrats.

Nobody "Needs" to know anything about racism.

it's not, really. It's sufficient to be sure you are never racist NOW. Because we can't change the past but we can change the present and that can impact on the future.

Racism started at the dawn of time. It is always 'them vs. us.' It will end at the end of time. Do feel free though, to chronicle the entire history, from caveman on.

It isn't and most of it is lies.

It is to avoid repeating the mistakes relating to racism and to tell our future children the struggles their ancestors had to go through that leads them to their present.