Christopher Columbus was a cartographer and explorer, nothing more; besides, all European nations at that time had swelling pride, and thought their cultures "superior" compared to other cultures.
This probably isn't even in the top twenty racist ideas to contest, but I guess it has some manner of truth; The Settlers eventually destroyed Native American culture.
However, racism is a completely different concept today. In today's world, the vast majority of humanity isn't racist. It's now more of a crime to be racist than it was then.
So, why not focus on stopping the KKK or something rather than talking about this? It's not a pivotal topic compared to what is to come and what is happening now, and Colombus played little role in it anyway.