Why do some people find it more ethical to kill and eat plants rather than animals? Why should I value animals more than plants?

I've thought about this. What if there are intelligent plant life forms somewhere in outer space that take great offense to us eating plants? It could be that there are no such life forms and plants aren't even considered life. We'll probably find out when we start encountering aliens. But until then, I'm eating.

First , plants and warm blood animals have two different definition for death in medicine. Second, you need nervous system to feel pain. Animals have it but plants don't. Conclusion Even if they feel the pain I don't know what ethical means in the nature It's unavoidable As a part of this nature human being cultivates plant and animal even THEMSELVES for meeting their needs.

I think its what the society has accepted via words like "Butchery" for killing animals. If killing animals is fine, then why was there so much brouhaha for the Yulin festival? The meat industry uses the most torturous and bizzare methods to grow cattle and poultry. Isnt that hypocrisy? Plants dont have legs, hands, brain, liver etc like us. So both shouldnt be compared. Especially Mammals have been found closest to humans in the way they live and reproduce. So killing Mammals is almost like killing humans.

History of cultivating plants is far more older that history of animal farming. This made killing of plants which can be cultivated comparatively more logical during ancient times. At the origin of religions this fact is recognized and many religions discouraged killing animals. which later became basis for the ethics that killing plant is more ethical than killing animals. In my opinion cutting a tree that can't be grown easily is equally bad as killing animal. It is not ethical until you restore the balance of nature.

May be Ms Adriana Heguy might have got the most satisfying answer to her quest but here I have something to say apart from scientific proven facts? Don't be surprised to further reading as whatever I am going to write is basically very difficult to digest until unless one has never heard a word like 'karma' and 'reincarnation'? Karma is an action of someone by  'words, action or mind' (we call it  'mansa vaacha karmana') ie to hurt by words, physical hurting, or thinking ill of others. In every case an impression is recorded on the 'hard disc' of soul. which will be judged by the 'higher authority and shall decide to 'compensate' in equal measure, good for good and bad for bad. That equalization is settled by forming one's DESTINY in ones reincarnation ie next birth. Good deeds bring an destiny more of happy chapters and some bad deeds, which every one is bound to commit knowingly and unknowingly, bring painful chapters of life. You may be wondering where does eating Veg or Non-veg fit in this explanation? Well read further in details as this was written to make things easy to understand what I am going to write further in connection with your question.        Wise men tell us that all kind of life was created made of basically five elements,earth, water, fire, air, and ether. No live body exists other than of these five elements. And there is five kind of life (bodies) in this universe. Plants are made of basically water and other four elements are for name sake, then come snakes, scorpions, ants etc which are having two elements mainly earth and fire and the rest three elements are dormant for all practical purposes, then is bird kingdom mainly with active three element mainly earth, water and air and having other two element in negligible quantity, then come the four legged animals which are having earth, water, fire and air mainly active elements and ether to a minimum quantity according to the evolution of their soul? (every life is having soul of the same type and is evolving towards human body which is the only gate to get salvation from the cycle of rebirth which you may call resurrection or born-again)  Now in nutshell, the life which is having as many active elements and if we destroy that body we accumulate sin according to the type of life. If we destroy one element active body we add to our sins but much less comparatively to if we destroy a body with two active elements? So our bag of sins will keep filling much heavier if we destroy four legged animals and it will be unbearable if we kill human being then only law of nature is tit for tat? So the wise men told us to eat only VEG foods because devil, mind it not GOD, devised this body which can only sustain on eating life. That is why I wrote in the beginning that every one is bound to commit sin and this is perhaps the Original Sin also. So we eat only Veg food because we should accumulate minimum possible sin and we become slave of sin until unless we don't pay back in the same coin. Well! We can say this world is a bank, our life is a debit card, and our deeds are the currency deposited, our breaths are validity for this debit card and the day total deposit (destiny) has been withdrawn the debit card is BLOCKED till one is born again and new destiny is formed from the 'stored karmas' (accumulated sins). One may not believe but certainly can enjoy reading but one's believing or non-believing does not change the fundamental truth of this creation and this is the knowledge of our Masters who speak only what they see.

Humans also is a kind of animals, but can't say it's a kind of plants, although humans will kill and eat one another, but compared with heterogeneous isn't much more comfortable and ethic

There's no single or common motive for vegetarianism. I'd add that your questions do not necessarily follow one from the other as you don't have to value animals more than plants to not eat them for ethical reasons. My reasons are two-fold. 1) I worry about man's impact on the environment and animal agriculture has been identified twice (to my knowledge) in UN reports as either the single biggest, or joint biggest impact on the environment and the biggest single/joint contributor to greenhouse gas emissions. The other is transport. It is incredibly simple for me to not eat meat. It is much harder for me to opt out of transport and the other major contributors to environmental degradation. 2) I worry about the welfare of animals in agriculture. Modern food distribution and marketing has distanced most of us from our food sources. It's simpler for me not to buy or eat meat than it is for me to go to the lengths it would require for me to be able to make confident and informed decisions based on provenance and animal welfare.

Okay. Lets get this straight, we  humans feed or go for something that is abundant, more. You eat hen's egg but not ostrichs because they're easily available. I'm not saying meat is inaccessible but vegetable are available in more quantity+less costly. I drink cows milk because cows are more in quantity than buffalo or goat. U see when there'll be scarcity of vegetable, human, we, me would go by next most available source, namely meat, animal or byproducts. Another thing, its easy to grow plants. 4 weeks? 2 months? And what you need is seed(s)+water, land in least cases. You just cant grow meat just anywhere, that too in huge numbers. Another one, plants/vege/fruits can be washed & they'll be as healthy and tasteful. But what if egg us contaminated what if the chicken were sick? Next, religion. Some/many religion discourage it.

There is nothing wrong with killing and eating animals. We're assuming that doing so does not cause gratuitous pain and suffering, that the species is not endangered, a crucial part of a biome, etc. There are no doubt other qualifications needed, but by and large, there is no problem. The fact that it is not necessary to eat meat is neither here nor there. It is not necessary to ride a bike when one could walk, but that does mean it's wrong to ride a bike. Life (whether in plant or animal) is a conditional good, i.e. it has no value in itself  but rather it is a condition of things that are good in themselves such as taking pleasure in morally good things. It is wrong to take pleasure in the infliction of pain and suffering. A life of pain and suffering for an animal is not a good thing for that animal. That's why we take the life of (euthanize) animals that are in pain or suffering. Being a vegan or a vegetarian is just a choice. There is nothing morally superior (or inferior) about it.