Time to just live with it.

If you have a lever operated waste and overflow, remove this mechanism.
Using a dremel or similar cutting device, I use a sawzall, carefually cut the drain and threads in two places about 1/2" apart. With a screwdriver, pry this section out. When this is done, collapse the remaining section and remove.

We're living parallel lives! I posted the same problem last month at the link below. I found out that there is a wrench that will do it, but there was some concern that it might disturb the old plumbing in the walls. I was then told that it could be cut out as mentioned above. The guy at the plumbing supply place kept repeating,"just don't cut into the tub", which didn't do wonders to inspire confidence. I dried it off really well, masked the area, applied some chrome paint, and bought the Flip-it tub stopper(which only leaves a narrow rim showing around the outermost edge).

Except for being taken out when I clean the bathtub, it now lives in that drain forever!

Good luck with yours!

Here is a link that might be useful: Rusty Drain Flange