I came up with a compromise. The city can should the mural, but add an explicit anti-slavery message to it, something like: "We remember the horrors of slavery and other atrocities towards this nation's indigenous population." Then, the context can be clear. I am actually as facetious about this as I am serious.
This is VERY obviously the common sense solution. We could quibble about the exact wording, but other than tjat it's a cheaper smarter better option.
It would only cost 300k.
If you actually believe the contractor costs to fix this mural is 600k you are insane.