Well, I'd say it depends on what you are trying to accomplish.
If you don't agree with his political stance and and want to loosen his outsized influence on US democracy (e.g. by pouring hundreds of millions in political campaigns, silencing intra-GOP opposition by threatening to primary them with his money, using Twitter to push the fringe talking points of the day), then I would argue your goal should be reducing his net worth by refusing to buy from companies he's invested in.
If on the other hand, you're mostly criticizing that the quality of Tesla's cars suffers because the company doesn't get his full attention, it's a different story and your stance makes sense.
Your idea, while well-founded, is practically impossible. If he put all his money into the S&P 500, and I refused to do business with any of its constituent companies, I’d barely be able to enjoy the fruits of modern society. I’m not that principled.
As for the second point, I’d contend that the quality of Tesla’s vehicles is suffering in large part because of his direct involvement. Choices like substituting a yoke for a steering wheel and the design of the Cybertruck were his ideas. And I wouldn’t be surprised if the latest idiotic move of eliminating steering column stalks for the turn signal, lights, and windshield wiper and washer were his, too.
If you don't agree with his political stance and and want to loosen his outsized influence on US democracy (e.g. by pouring hundreds of millions in political campaigns, silencing intra-GOP opposition by threatening to primary them with his money, using Twitter to push the fringe talking points of the day), then I would argue your goal should be reducing his net worth by refusing to buy from companies he's invested in.
If on the other hand, you're mostly criticizing that the quality of Tesla's cars suffers because the company doesn't get his full attention, it's a different story and your stance makes sense.