Anyone who has been vegan for more than a minute has probably encountered some jerk attempting to punch a hole in your argument for veganism with gems like "Don't you care about plants?"or "Plants feel pain too!" and most recently "Some cultures believe plants have souls."
In my experience it's rarely a legitimate discussion someone is looking to have with you and it's perfectly appropriate to ask "Do you actually want to engage in a realistic conversation about this or are you just being snarky?" I feel like when I'm getting questions about veganism it's like turning a light switch on where I go into activist mode as my brain starts to prepare for the barrage of questions I'm about to have to answer. Before getting into the mind-set that I'm about to get verbally assaulted, I like to make sure I even need to bother mentally preparing. I also find that asking if someone is being serious is a great way to subtly point out that their comment/question/statement was sorta rude or silly. If the person is genuinely asking or commenting, I offer you these quick comebacks in response.
- If you really care about plants, plant souls, deforestation, etc., a plant based diet will save/spare markedly more plants because we're not feeding them by the truckload to herbivorous animals so that they can become our food.
- Science (and logic) has proven that animals suffer and feel pain. At such a time that science proves broccoli has a central nervous system allowing them to feel pain I will re-evaluate my diet.
- I expect that with your concern for plant sentience you are no longer cutting your grass, buying flowers or eating any fruits or vegetables yourself. How is that going for you?
Any one of the above responses will let the person know you can easily shoot down anything they could possibly ask.