If you're anti-Tesla due to your experience with and observation of their product, legitimate reasons like that, that's not a conflict of interest. You're not starting out with a bias. You're allowed to form an opinion for the right reasons and bring it forward without it being suspect.

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.