Consumer Edge analyst Jamie Albertine, who is bullish on Tesla and has a price target of $385, said the company's financial results were in line with his expectations, but Musk's attitude on Wednesday's conference call is a big issue.
"We totally disagree with the way Elon handled himself," Albertine said on CNBC's "Squawk Box" on Thursday. "It's an incredible red flag and we are re-evaluating our stance on the company as a result."
Tesla shares were down about 7 percent on Thursday, trading around $280. Tesla representatives were not immediately available for comment.
Musk interrupted two analysts asking questions on Wednesday night's conference call after Tesla reported a first-quarter loss that beat expectations. He referred to one analyst's query as a "boring bonehead" question, said the "dry" discussion was "killing" him and then had a lengthy exchange with a Tesla shareholder and blogger on several topics, despite Tesla's normal rule of allowing only one question per person.
The call marred what otherwise was a good quarter with some positive signs, Albertine said.
Albertine said that although Musk simply seemed frustrated, his behavior fueled Tesla "naysayers" by making him look "unglued or unhinged."
Musk has to remember that in some way he works for the shareholders, Albertine said, and the analysts are acting as the voice of Tesla's large institutional investors on conference calls.
"I thought it was disrespectful and inadvisable, and I have never in my career certainly have heard any CEO act that way," he said.