Nathan Bedford Forrest was not the, or a, founder of the KKK. He was drafted --- in absentia --- to be the figurehead CEO to lend 'credibility' to a group that was already amassing a sleazy reputation. Less than two years later however he did officially disband it.
Meanwhile the crucial phrase sits right there in your OP and you're oblivious to it. That is, "from city parks". That's what the city would have done with its own property and indeed what the new owner did with their own property. And it's also what the various other municipalities have done, including New Orleans, including Charlottesville.
Meanwhile, a ways east of Memphis in the town of Pulaski, where the United Daughters of the Confederacy (the group who ran around putting up all these revisionist history transmitters in various city parks and public spaces during the Lost Cause craze in the early 20th century) --- affixed a plaque to a building at 205 West Madison Street to commemorate and name the six ex-soldiers who actually did found the Klan (Maj. James Crowe, Calvin Jones, Capt. John B. Kennedy, Capt. John Lester, Frank O. McCord, Richard Reed, none of whom were named Forrest). When that building was sold to a new owner in the 1990s the new owner turned that plaque around so that it now faces backwards with a complete blank, symbolizing that Pulaski "turned its back" on that legacy.
And yet ---- it did nothing to destroy the history of that founding, clearly it didn't since I just related it to you.
In ALL of those cases the owners of the property chose to divest themselves of those propaganda transmitters, which was and is their right to do, and there's not a damn thing in the world you can do about it.