I used EXACTLY the definition I gave. Yes, you insisted on an extremely narrow legal definition of "slander", since I was not writing a legal brief, I used a common, broader definition, Mr "The Turing Machine Is Another Name For The Turing Test".

I just looked, and Chambers Dictionary is on-line. See http://chambers.co.uk/search/?query=celebrate&title=21st definition 3.

Now, that we have cleared away that Red Herring; why do you want to honor traitors who stood four-square for slavery, segregation and white supremacy?