Okay now you're the one getting into pseudoscience. What is sentience in your book? People disagree on what sentience is exactly but I think at a basic level it's the ability to experience feelings or sensations. The process of touch is associated with our sensory organs and nervous system. First our peripheral nervous system or sensory nerves activate to stimuli and send signals to our cns or brain where we process those signals. Of course that's a basic explanation but "consciousness" or "sentience" requires a complex nervous system to process that information and generate awareness.

As far as we know plants lack that ability to process information. Of course plants react to stimuli as they're living as you said. For photosynthesis, it does not require any decision making or sentience. This communication you see are non-sentient responses relying on things such as gene expression. So anyways, I don't understand the purpose of your generalizations on vegans. I'll say it again, they are ignorant people in every community and in no way does that reflect the whole community.

For your last argument, veganism isn't about whether or not we're omnivores and we don't rely on your opinion on whether or not veganism is unnatural.

Based on our understanding of biology, a prerequisite for sentience is a central nervous system. Plants have really amazing abilities to pass chemical signals, but they lack any mechanics that would allow them to internalize the signals they receive. For example, I wouldn't say that my doorbell is sentient just because it can warn me when someone is at my door. Importantly, animals are different from plants in their ability to internalize pain, fear, sadness, etc. This is why animal ethics and welfare are considered important discussions, and why it's damaging to invoke plant sentience to distract from that discussion.