People making the argument that plants feel pain may not realize they are being illogical.
Try to give people the benefit of the doubt and clarify which logical fallacy they applying. "Plants feel pain too," is a False Equivalency.
Instead try stick with the evidence that eating plant-based extends life, decreased rates of obesity, and decreased rates of chronic disease.
When you engage in someone else's logical fallacy it hampers the true goal, which is to understand one another and communicate more effectively.
For a list of Logical Fallacies see https://www.vanderbilt.edu/writing/resources/handouts/illogical-arguments/
If you would like to read an excellent article on how scientists know plants (which lack nervous systems) do not feel pain click here
https://sentientmedia.org/do-plants-feel-pain/
Here is a science article from NCBI on plant signaling https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2633694/
Thank you for the question I hope everyone reads more from Seth Millstein if they are interested in health and veganism.
https://sentientmedia.org/author/sethmillstein/