I don't think it's right for an employer to do this. The president has a lot of power, but the fact is that he can't do most things without the approval of Congress -- or the courts. So to tell your employees that Obama getting elected is going to be the death-knell of your industry is just flat-out lying. Obama can't do that alone. Neither can Romney. And even if your industry is "wiped out" there will be retraining programs to help those people get into other industries; you might actually end up better off than living as a coal miner.
David Letterman is retiring. Such great memories of watching him over the past thirty-two years!