Elon Musk’s SpaceX is facing protests against its expected initial public offering from some of the same advocacy groups that helped erase $600 billion from Tesla’s market cap early last year. SpaceX’s IPO is poised to be the largest ever, raising tens of billions of dollars for the Musk-founded company and valuing it above $2 trillion. If all goes as intended come June, the conglomerate that now owns a rocket manufacturer , a social media app , and an AI chatbot developer will instantly rank among the world’s top 10 largest publicly-traded companies. On Wednesday, Randi Weingarten, president of the American Federation of Teachers, wrote to the US Securities and Exchange Commission urging it to scrutinize SpaceX’s IPO preparations. The company’s shares are likely to end up in the retirement accounts of the union’s 1.8 million members who come from education, health care, and government.…