You did your job, and should feel no guilt. You could have gone to the other executives and board, but having been in the same boat I can guarantee your odds of

You did your job, and should feel no guilt. You could have gone to the other executives and board, but having been in the same boat I can guarantee your odds of success would have been slim, and your odds of being pushed out good. If you were super skillful and political, you might have been able to approach key execs and ask them if your questions had been adequately examined, and maybe someone far higher than you in the company would have taken up the torch. As an aside, this is a great example of crappy managing. A good manager should prize getting opposing opinions. This person valued getting their ideas implemented more than they valued making the best decision for the company. As you saw in your meeting, it's incredibly intimidating for rank and file employees to publicly disagree with managers. You were special because you did so, and that kind of public honesty should always be encouraged and cultivated in good organizations.