Answer:
Is bluffing ethical? Under what circumstances?
Bluffing is basically lying, and lying is wrong. But on some circumstances, specially when you are carrying out a game strategy (and want to win), then bluffing might not be so bad.
Personally, I believe that bluffing is not unethical when you are negotiating with unions. I have nothing against unions, but their duty is to get the highest possible salary and benefits for their members. On the other hand, the company must balance the interests of its employees, the community and its shareholders. Union delegates always make very high initial demands, the company offers a very low increase or raise, and then after negotiating you get to a middle point. So bluffing could be just a strategy in order to negotiate some concessions, e.g. no pay raise until the company starts making a profit again.
What would Kant and Mill say?
Kant believed that the morality of someone's actions should be judged based on their duty. Since it is your duty to try to get some labor concessions, then bluffing is not unethical.
Mill believed that the morality of someone's actions should be judged based on the results, or how much good or happiness results from them. In this case, I suppose that more people would be unhappy than happy if you actually get some labor concessions, so bluffing would be unethical.
What would be the result under the Front Page test?
The front page test basically wants you to look at the events from the point of view of a third party that is not involved in the actions. If you could read this on the front page of a newspaper and it happened to someone else, would it be ethical or unethical? Since I believe that bluffing is a valid game strategy, then if I read this on a newspaper I would be OK with it.