But it wasn't slave labour. It was constructed by highly skilled craftsman who seemingly enjoyed better living standards than their non-pyramid constructing equivalents.
That's dumb, I'm sure some think that because of racism but that can be said of anything. I think for most it's due to the mystery about their construction that still remains and the seeming impossibility of moving huge numbers of truly massive blocks 6000 years ago. If it was an equivalent sized castle or something built with blocks that could be carried by one or two people there would be less motivation to look for crazy explanations.