If they don't have any value, then you shouldn't have any problem with them going away. You obviously consider them valuable, or else you wouldn't be defending them.
Indeed the right to buy a stock is valuable, but as an employee / the state you should postpone the taxation to when the value is actually retrieved by the person you tax. It's a bit like saying 'You're house is worth X, you should be taxed regarding this price, even if you don't have yet made any profit'