A reader counters Michael Marder:
If anyone is silly enough to think that plants can suffer the way we animals can, then that person had better eat plants and nothing but plants. We have to feed an animal about ten calories of plant food to produce one calorie of animal food. Animals are calorie factories in reverse. We can save the lives of about 90% of the plants we now kill if we don't waste them by feeding them to animals first.
Another points out:
There's a huge difference in the morality eating plants and animals. First, most of the plant food that people eat are created by the plants with the intention that they be consumed.
Fruits, vegetables, legumes, seeds, nuts – these are created by the plant to entice animals (and people) to consume them in order to spread the seeds so that the next generation of plants can live on. Although we don't quite sow the seeds in the way other animals do (by passing them through the gut) we do accomplish the same thing: consume the fruit, plant the seeds, and perpetuate the species.
Second, for many plants, fruiting is the end of their life cycle. When you harvest wheat or tomatoes, those plants are essentially dead at that point, having expended all of their energy fruiting and not robust enough to survive the winter. It's not like animals which are cut down in their prime.
Third, many plants don't die at all. Vines, fruit and nut trees, pineapple plants – these are all cared for and nurtured through many successive harvests. Eating something like lettuce is equivalent to eating a chicken: you're killing the plant in its prime to consume it. But overall, the vast majority of plant consumption has nowhere near the ethical dilemma caused by eating meat.
Another takes Marder's stance to its logical extreme:
Our bodies automatically slaughter millions of bacteria on a daily basis without us eating one thing. You could go on a hunger strike and still be on an endless murderous rampage. If you really object to all this wanton killing and want true and complete moral purity, suicide is your only option.