Thanks so much for raising this important issue, and likewise a vitally important question in connection to it. 
I must say, I really have to disagree with this interpretation, she strikes me as simply being very matter of fact. Direct talk isn’t necessarily angry talk.
As it happens, just the other day I watched a truly uplifting panel discussion in which Thunberg took part:
One of the things that really struck me about the conversation, was the thoughtful, warm and understanding qualities that characterized it. One detail in particular that I found so heartening to observe (having grown incredibly weary of the grizzly, ‘blame-y’, aggressive tone of so much of our public discourse) was Thunberg’s comment that, to paraphrase: people aren’t evil, they just don’t know. To me there is such an admirable compassion underlying her approach to the issue.
Turning to your extremely important question, again, just the other day I watched the most inspiring interview with Venerable Analayo within which this exact issue was raised. By preference, I’d just post a link to that video because I couldn’t put things a fraction as well as he did, but unfortunately the host of that content has put it behind a paywall (finding this deeply unfortunate, I’ve written to ask if they have plans to make it public).
As an alternative, I’ll quote from his 2019 paper A Task for Mindfulness: Facing Climate Change (again most unfortunately, behind a paywall):
Another type of reaction to the crisis is anger. As just mentioned, some leading politicians and high-level executives are actively working to prevent appropriate changes from taking place. Yet, getting angry with them is not a solution. For one, to some degree, almost all human beings contribute to the problem. Let the one who has never driven a car, taken a flight, eaten food imported from abroad, worn clothing manufactured in a distant country, etc., throw the first stone.
Besides, at least from an early Buddhist perspective, even righteous anger is a defilement of the mind. There is definitely a place for stern and strong action, but this should better come with inner balance rather than aversion. Inner balance is crucial for any possible activity to achieve maximum benefit. From the viewpoint of mindfulness practice, getting angry equals succumbing to one of the root defilements and thereby to what has contributed to and sustains this very crisis.
Anger is a problem and not a solution. A solution can only be found when the mind is not clouded by defilements and therefore able to know and see things accurately. The Satipaṭṭhāna-sutta and its two Chinese Āgama parallels list anger not only as a state of mind under the third establishment of mindfulness but also as the second in a set of five “hindrances,” called such because they hinder the proper functioning of the mind.
In case of interest: