I've successfully reshaped bent BNC connectors by using hollow punches like this:
http://www.harborfreight.com/9-piece-hollow-punch-set-3838.htmlStart with the smallest size that will fit but use a size that will slip over the center insulation. 3/16 inch is about right. Maybe a few
gentle taps with a 1/4 inch punch to finish. Go slowly and don't use a sledge hammer. The metal is soft. Don't let the sharp edge of the punch cut into the center insulation in the connector. You're using the tapered outer surface of the punch to gently bend the metal of the connector back to a round shape. Test the fit often with a BNC male connector to see how you're doing. If you spread the metal of the female connector too much it won't fit and you'll have a harder problem to deal with.
Your connector looks like it should be an easy fix.
Ed