Elon Musk is set to join Donald Trump as he returns to Butler, Pennsylvania.Susan Walsh/AP. Evan Vucci/AP.Elon Musk revealed Tesla's new robotaxis hours after Trump said he would "stop" AVs from operating.Trump expressed concerns about autonomous vehicles at the Detroit Economic Club.Waymo, GM's Cruise, and Zoox are also advancing autonomous vehicle technology.Elon Musk has become one of Donald Trump's biggest supporters, but he might have to convince the former president not to kill a major part of Tesla's future.During his remarks at the Detroit Economic Club, Trump said he found autonomous vehicles "concerning" and promised to "stop" them from operating."I will stop Chinese — and other countries — produced automobile and autonomous vehicles," he said.