This is a very common problem with the 1911 bushings. The manufacturers simply fail to either use Loctite or to stake the bushings properly.
You have options:
1. Just grab the bushing with Vise-Grips and remove the screw. Buy a new bushing.
2. Clean the bushing threads and the frame hole threads with a solvent to remove the lube. Apply a SMALL drop of Loctite BLUE (temporary) to the frame threads and screw the bushing back in. Give it 24 hours to fully cure, then try to unscrew the screw.
3. Brownell's sell a special tool to grip the bushing with that won't damage it while you unscrew the screw.
However you get it off, buy a grip screw bushing driver bit from Brownell's.
This is a hollow tubular driver that surrounds the bushing and supports it so you won't damage them while installing or removing the bushings.
Check the bushing that's out and look at the one's still in for signs of any type of Loctite.
If you see Loctite, use a soldering iron to warm the bushings until the locker softens, then use the special driver to remove them.
If the bushings are staked, turn them out a slight turn then turn them back in.
Continue turning them in and out, each time a little farther out.
This will "iron out" the staking and allow removal without stripping anything.
Once you have all the bushings out, use lacquer thinner or Acetone to clean the bushings and the frame holes of any old thread locker or lubricant.
Allow to dry, then apply some Loctite RED (Permanent) and use the driver bit to screw them in the frame tight.
This will eliminate them from backing out again.