The claim here is that eating animals is justified because killing plants still represents taking a life. Alternatively, plants release chemicals when cut and therefore know they've been cut, and therefore are suffering somehow.
The vegan position only has anything to do with "taking a life" since it has to do with the suffering and well-being of conscious creatures. Animals are conscious and can feel pain. Plants are not and cannot. They have no nervous system, and therefore we have no moral obligation toward them because we can't impose needless suffering on them.
My doorbell rings when someone presses it. Does that mean that my doorbell "knows" someone is at the door? No, it's an automated response, which is not an argument for moral obligations toward doorbells.
You lose an energy factor of about 10 when you eat the animal that eats food than eating the food itself. So even if the previous arguments didn't hold, you'd still be looking at a much higher death toll from animal products than plants. You should still go vegan.
Why is Dominion so hard to watch but mowing the lawn isn't? It's strange to say that if you're watching an animal get violently stabbed to death struggling in fear, you'd be unable to make a clear distinction between that and picking a flower and handing it to someone. This argument really does sound like it's made in poor faith.