I will happily "judge" that you had no right to the loaner after they asked for it back. The term you are reaching for on that is "Theft by Conversion."Edit-unless you've had your brand new Tesla die twice on the side of the road only to have Tesla tell you there isn’t a problem twice, you probably shouldn’t be judging somebody else’s actions, especially if the actions solved the problem.
Beyond that, your issues with your vehicle and Tesla are yours, and I am glad they eventually resolved them. But I will, today, tomorrow and any other day be happy to judge the actions you have already stated you took on that particular point. You were wrong on that point - you had other legal options, but refusing to return property is theft, literally by definition, and it is not one of the ones you should have taken at all.
I doubt it actually speaks to your general character - you were frustrated and obviously unhappy with the situation - but it still was not proper, correct, or even legal. It is also not conduct you should be encouraging other people to mimic.