Where people get the idea that senior management is infallible is one of the great mysteries of life. Senior management doesn’t expect that all their ideas will be great, but they do expect that you will respectfully help them achieve the correct outcome.
This means that if their idea has flaws, they expect you to demonstrate your understanding of the outcome they desire and then candidly discuss whether their idea supports the outcome or not. Remember that senior management has usually made it to the top because they have an astute ability to gather information and determine what things to take action on.
What they don’t expect is for you to give them false agreement or disgust with their idea.