TruGreen ChemLawn stopped using "ChemLawn" in all but a couple of locations in 2007. They, from what I'm told, encourage the use of the name incognito.
They dropped the name because of the association of ChemLawn with poisoned playgrounds. The trademark is abandoned now, almost 20 years later.
The point being, CF saw the value of the name Six Flags, even with all the negative connotations in the investor community, the industry and the enthusiast community.
Hopefully, when the ship rights itself, the name will have either redeemed itself, or they retire it.