Given that plants aren't conscious and do not feel pain, any line of reasoning that is predicated on the assumption that plants are conscious and feel pain is irrelevant.
Your argument is just antinatalism, but for farm animals. Every animal will suffer in its life. Eradicating an entire population to reduce suffering is pretty extreme. Other arguments for veganism, like the environmental one, are much more palatable.
Where, exactly, did I argue for the eradication of an entire population? Ending the exploitation of animals does not require eradicating them.