There's usually a tiny bit of end play in the shaft that goes through the switch. One thing you can try (very very carefully) is to pull the switch outward as far as that end play allows, and put some kind of shim behind it. Then tap the end of the shaft (that is the steel shaft, not the hollow shaft of the switch) with a small hammer. The idea is to break the bond, not to remove the whole switch at once. You might even have to push the switch back down and repeat the process to get it free enough to pull off. The main caution is that whatever you do, you must work slowly, and never exert more force than the switch can handle. If you get impatient, remember how much a new switch costs. Very few of us work for more than that per hour.