A holiday to honor someone who owned hundreds of slaves for over 50 years,

[Kurska]

25. If you grow up on a society where slave owning is common

It is encouraged and held up as a morally justified thing to do. If you have means you are more than likely to own slaves. People don't understand just how much their morals are shaped by their social context. There wasn't a large abolition movement in the united states when Washington was alive. Is it a moral failing that Washington didn't embrace abolitionism until the very end of his life? Yes. Does that eliminate everything he ever did for this nation (like not assuming absolute dictatorial power when he probably could have). No.

The reason John Adams didn't own slaves was because he grew up in a Northern culture where it wasn't common and wasn't economically viable. I don't think it was just because he was a better man than Washington.

It is really easy to look into the past and hold people in judgment for not measuring up to modern morality. I'm sure just about every president we have ever had was a homophobe for instance. A great deal of them were probably anti-semites or very racist. Thats the social context they grew up in. If you want to damn them for it, well that is your call.