I can think of a lot of things other than Confederate flags, I was making a symbolic argument against your misuse of the word bikeshed.
Slavery is a bad practice and I would definitely not work with someone who felt otherwise, but other than that, your argument is just worthless escapism. Have fun talking to HR in the future.
My point was that trying to paint slavery as being particularly objectionable in the face of just as seemingly reprehensible (but not at all in context) metaphors of child murder, is disingenuous and pointlessly selective. Child murder and slavery are horrible and I can't believe I actually have to specify this. They are both ongoing, so your argument from ancestry doesn't work. There's millions of slaves as we speak, many more ancestors of slaves and many who have had their children murdered. That doesn't somehow make those metaphors irredeemable when put in purely technical context, e.g. slavery as a relationship of total control and ownership by one party over another (actually just as applicable to S/M -- a consensual sexual practice, as it is to real-life slavery).
Slavery is a bad practice and I would definitely not work with someone who felt otherwise, but other than that, your argument is just worthless escapism. Have fun talking to HR in the future.