Tesla chief executive Elon Musk became involved in a dispute with Bernie Sanders on Sunday after the US senator demanded the wealthy pay their "fair share" of taxes.
"We must demand that the extremely wealthy pay their fair share. Period," Mr Sanders, 80, wrote on Twitter.
Mr Musk responded by saying: "I keep forgetting that you're still alive."
The billionaire chief executive offloaded $6.9 billion worth of stock in the electric car company as of November 12, after asking his followers if he should in a Twitter poll.
About 57.9 per cent of people who voted said he should.
"Want me to sell more stock, Bernie? Just say the word," Mr Musk posted in a follow-up tweet.
He is a notoriously belligerent tweeter but his words were injected with extra venom just days after his net worth fell by $50bn.
Mr Sanders's demand comes amid Washington's efforts to raise taxes for the super-wealthy.
US Senate Democrats have unveiled a proposal to tax billionaires' stocks and other tradeable assets to help finance President Joe Biden's social spending agenda and close a loophole that has allowed them to defer capital gains taxes indefinitely.
