Are you that dense..Sentience isn't a deciding factor, unless they display human like ability, intelligence and ingenuity.
All things react to stimuli even humans, that's why the example is flawed. Biological matter has it's own DNA, cell structures, which determine how it reacts to us. In fact some would argue plants do the opposite to us (convert carbon dioxide to oxygen) and keep us alive, therefore we should consume animals since they are a competitor on the planet.
"even humans" well, no sh1t, all sentient beings react to stimuli. Not all inaminate objects do. Could've picked another example.
Sentience is the main focus point as though you made a jestful remark comparing a few dozen chickens as less deaths then that of a thousand plants. Those few chickens will have suffered. The plants wouldn't have. Intelligence matters not. Sentience does. My puppy is a dumbass compared to the two kittens I had a long time ago. Yet, it feels pain when its hurt. Punch a wall or slap a plant, there is no suffering. Do I really have to lay this all out for you?
Now ask yourself if you couldn't go to the supermarket anymore as the apex predator you are, and you had to kill or artificially inseminate/rape every animal you ate or milked from, would you really? And lets broaden that question to the entire human population. If everyone had to do the above by their own hands, how many people would keep eating meat and dairy products?