What does it say about a country to support a person/holiday such as Colombus?

I think celebrating a holiday such as Columbus Day is very wrong. I believe it's demonstrating to people that it's okay to celebrate the deaths of thousands or even millions of people. We shouldn't be celebrating the actions of Colombus because many of the things he did was terrible. For instance he made Native Americans into slaves, sent them to Europe and on the way there many of them died. He used people to increase wealth. I do understand the fact that if he hadn't recorded America I may not be here today, so why don't we celebrate the founding of America and not Colombus? I think that would be a better celebration, we would simply be celebrating the founding of America and not celebrating the horrible actions of a terrible man.