How bent is it? If it more than a little, the metal is probably pretty
shot. If only a little, it can probably be saved.
My boat hoist was bent up by ice two years ago. I cut out a 6x6 so that it
fit over the pipe properly, and hit it with a sledge hammer. It got 80% of
the bend out and works okay now. (looks like crap, but works...)

I would suggest combining the two ideas. Gently pull on a chain above the
bend, and hit the bend with a sledge hammer at the same time.