Stocks go up but bond yields don't, US pensioners usually rely on bonds not stocks.
If that is true, then I am wrong and sorry for that. The 1 billion per year sale still represents only around 0.5% of his net wealth. And in case the tax is increased, there is a good chance that he will postpone his plans to sell these stocks.
Now another proposal that has been suggested by some of the Pacific Coast Democrats is to tax unrealized capital gains. They say that this will prevent people like Bezos sitting on top of $200 billion worth of stock and still paying zero tax on it. But now comes the important question. Perhaps you are implementing a tax on unrealized capital gains of let's say 4%. Bezos need to pay $8 billion as tax. But there are a lot of people who have unrealized losses. If the government is taxing unrealized gains, then they need to reimburse (a part of) the capital losses as well.