Actually, I think she would be right to say it's a metaphor. All other things being equal, I would say it's silly to say this is a "call to violence". Unfortunately, as you point out, all other things are not equal. Sarah Palin could never have gotten away with this. I never know what to do when a liberal makes a (relatively) benign statement that a conservative would have gotten roasted for. Instead of interpreting the statement the way a liberal would if a conservative had said it, I think it's probably better to just point out the double standard, as you did.
McCaskill, we love you! What a loser.
Her words are seriously irresponsible.
She should not threaten the American people. We can agree and disagree on politics but don’t back Americans in a corner.