Well, I once heard someone say that when you look very carefully, you can see that every motion you make, every breath, every blink, has some effect on the universe. You can be careful not to hurt things as much as you can. You can swerve when a jackrabbit runs across the road. You can take care not to hurt people's feelings as well as you know how. But at many scales, both the very small and the very large, it gets much harder to see the implications of your presence in the universe. It gets impossible to predict or control. You can't stop wars alone, and you can't stop your immune system from murdering countless thousands of microbes every second. You are literally damned if you do, and damned if you don't.
And so, you "knowingly and willingly transgress," she said. You do your best, knowing that you can't avoid leaving footprints. And you accept that it's the way of things, and you love that.
Your question isn't academic, actually, even if plants have no sentience. Few vegetarians grow all their own food, carefully picking each bug off each plant through the growing season; they buy it in the store after it is grown and harvested commercially. Well, rabbits get caught in harvesters, mice get smothered in grain silos, and billions of insects are killed with natural pesticides even on organic produce. No food is really clean. Eating, life, includes death and there is no way around it.
So, I am vegetarian partly for humane reasons, but mostly for health reasons. I do really well on a vegetarian diet. I wouldn't kill an animal myself in order to feed me. But my son is not vegetarian, and I would kill an animal to feed him. So if it turns out that plants think and feel and write poetry, I guess I will go on like I do, and knowingly and willingly transgress as a part of the universe whether I like it or not.