Because we can all play this game. It's a very silly one, and I'm honestly concerned that the SEC, FCC, and other regulators have the same issue - the people who are suppose to be regulating companies have stocks, and those stocks affect their judgement in much the same way that Pelosi and other prominent politician-traders would never vote against their stock portfolios.
But, okay, let’s roll with that: after that video, you expect “the guy” to be long Tesla? There’s the avoidance of “conflict of interest”, and then there’s “I should not be left alone with large sums of money”.
The guy's twitter feed is basically one huge rant against Tesla and Elon Musk. He seems to have no other topic than that. Makes you wonder why he bought one anyway.
If you're anti-Tesla because you didn't think Elon Musk was funny on SNL, or you don't like his haircut, or some other unrelated reason, that's what would be unfair. But you can't write off anyone short on Tesla as inherently biased. Otherwise you'd be writing off all criticism period.