Sometimes freewheels are on REALLY tight, and the usual wrench/bench methods don't work. I grew up in the Eisenhower era and have removed a fair number of freewheels, but a few years ago I couldn't loosen a freewheel on a '90's mountain bike using the bench vise/bus driver method. I thought the freewheel must be cross threaded or corroded on.
I ended up putting the tire back on and waited for a friend to come over. We stood the wheel up on the floor, and put a big socket and 3/4" breaker bar with a 3' cheater pipe on the remover. I hugged the wheel to keep it from turning and he bounced on the end of the pipe. It took a few bounces, but the freewheel did loosen up. When I looked at the threads on the hub, they were very clean (with no sign of grease though) and in perfect condition; the freewheel was just on REALLY tight.
I have since taken off some freewheels using an impact wrench on the remover when I didn't have a vice handy.