> the only explanation I can come up with

Maybe you should think about it a while longer. Or find a friend who's better at coming up with ideas to help.

There are about a zillion other explanations. Maybe they think that "ANY messaging that encourages EVs dissuades the public from going public transport" and that's harmful. Maybe they see other EV makers as preferable to Tesla. Maybe they care deeply about global warming but just as you said, are letting their anger get in the way of that goal. Maybe they see the immediate harms of Musk's policies as a more urgent problem than climate change.

There's a tremendous leap between "Not supporting Tesla because of Musk" and climate denialism.