I don't see the line of thinking from anthropomorphizing plants to dehumanizing humans.
If anything the experience of getting in touch with Nature forms a powerful and undeniable basis for loving other humans, due to our shared existence within the unifying web of life.
In any event, I'm not anthropomorphizing plants, quite the opposite: I'm pointing out that humans are the anthropomorphization of the ambient natural "processing power" of living intelligence.
Without getting into to metaphysics of identity and the subjective "I"†, there is a result in cybernetics to wit: "every good regulator of a system must be (contain) a model of that system." Ergo, in a system under evolution we should expect models of systems to appear in those systems. In other words, a self-concept (of some kind) should develop in any stable evolving system.
http://pespmc1.vub.ac.be/ASC/LAW_MODEL.html
https://en.wikipedia.org/wiki/Good_Regulator
http://pespmc1.vub.ac.be/books/Conant_Ashby.pdf
So you have a system that includes many "I"'s and each of them is "running on" the same biological "wetware", so it's really not at all strange that they can communicate with each other, eh?
From my POV, this is filling in the scientific story for phenomenon that are common knowledge. There has been to time or place in human history without some people understanding and practicing the I-Thou relationship with Nature.
†(Gurdjieff distinguished humans from animals and plants as being "Three-brained" beings, as contrasted with "Two-" and "One-brained" beings.
Unity of the subjective "I" and God is a foundation of, e.g. Hinduism: "Atman is Paramatman." That "I" of consciousness is the "I" of all beings, including plants, animals, and ecosystems, as well as the Whole Earth.)
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Er, FWIW...
> To cut the story short: By speaking in the first person we can make statements about ourselves, answer questions, and engage in reasoning and advice in ways that bypass all the normal methods of discovery. As a result, we can participate in dialogues founded on the assurance that, when you and I both speak sincerely, what we say is trustworthy: We are “speaking our minds.” This is the heart of the I-You encounter.
This is incorrect. Scruton has failed to sound the depths of "I-Thou", "a relationship in which the other is not separated by discrete bounds". There is nothing linguistic in it. No boundary. As an example, consider that you can be in the "I-Thou" relationship with an infant.