He's not going to be able to sell his 9% stake at the current price without the market reacting negatively. The share price would drop because of the immense selling pressure it would cause. Unless there is another billionaire wanting to eat up all those shares, the supply would simply overwhelm the demand which in turn causes the price to drop until the market was able to meet the supply.
Another thing that makes this take over hostile. If it's rejected, Musk begins to sell his 9%, the stock price tumbles... and share-holders will sue the board.
I don't see how they don't have a fiduciary responsibility to sell here.
