That is an issue for the Madison city council and the voters of Madison to decide.
I’m not sure I’m understanding you but bottom line, he either has the power or he does not.
I suspect not. Now if the City Council voted to take this action that would be a different story but unless I missed it, there is nothing in the article stating that the City Council had taken any such vote.
Legally. But not morally. The descendants who come to the visit the site should have a say. After all some of the descendants of Lee don't want (and say Lee didn't want) the statues. Lee will remain in history. But when a dead prisoner of war has his plaque removed that's pretty much it, except the gravestone which doesn't explain anything.