I really wish that I could enslave white people
As a joke, right? What would you do to white people if you enslave them?
I will make their lives miserable and painful as I can
It's terrible to want to enslave anyone because slavery is morally wrong. You should never talk about wanting to enslave people, because others will be offended and hurt by that kind of statement.
It's just a joke, but why are you getting so offended?
That's good it was a joke, but your content is still very insensitive to the people who actually went through slavery. How would those modern slaves feel if their circumstances were made fun of?