Depending on what you are doing to the moulding, you could add a narrow block to the fence on either side of the bit so that the contact area is very small. That way the bow would be contacting only perhaps 4-6" of fence length (i.e. only 1 or 2 inches on either side of the bit). Unless the bow is pretty severe, that length should allow you to do what you need to do.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.