1. Are you aware how many animals (rodents, etc.) are killed in the processing of so-called "vegan" foods?
A goat is a pure vegetarian but you are eating that goat also. When you find a human being, who is a murderer, will you kill him directly or hand over him to the court? Assuming that the fish is also a murderer, you cannot kill it directly.
God will punish it. In the case of the fish, you need not file a case against the fish in the court of the God, because there is no need of such filing in the case of God. Moreover you are raising your voice against the hanging of a murderer stating, “If you cannot give life, you have no right to take it away”. You are also pleading that hanging is the most barbaric deed and that several countries have banned it. Your statement applies to the fish also, which is a murderer of the creatures. Life is common in the human being as well as the fish. Both are living beings. If you don’t have right to take away the life of a human being, you have also no right to take the life of the fish also.
The Dharma Shastras say that non-voilence is the highest justice (Ahimsa Paramo Dharmah). If you say that the fish kills the creatures for food and that there is no sin, there should not be sin if cornivorous hunters from forest enter the city and start eating the human beings. You should not object their food also, but you will kill them because your fellow human beings are killed. If you broaden your heart and see the fish as your fellow living being, you are practicing the highest form of justice, which pleases the Lord. You cannot compare the plants with animals and birds. Even in the case of plants, the green plants should not be cut.
Plucking leaves and fruits is not killing. The crops are cut only when they die after loosing the sign of the life, which is the Green Chlorophyll. In plants life exists but mind and intelligence do not exist.
Life is called as Pranamaya Kosa. Mind is Manomaya Kosa. Intelligence is Vijnanamaya Kosa. The life is only inert mechanism of exchange process of Oxygen and Carbondioxide and release of energy by oxidation. This mechanism has no awareness of the pain. The mind is represented by the nervous system, which is not present in the plants. The mind may be in very very primitive stage in plants as per the research of Mr. Bose. The ancient Indian sages avoided even plucking the leaves and fruits. They ate leaves and fruits when they have fallen from the plants (Swayam Viseerna Dhruva Patra Vruttita). They avoided this trace of sin also.
In plucking the leaf and killing an animal, the sin is qualitatively equal, but there is a lot of quantitative difference. One percent sin and hundred percent sin cannot be equated. Your argument concludes that if one does one percent sin, why not hundred percent sin be done? This equates to your statement that if one plucks a leaf why not we kill an animal. Are you pained equally if I steal one rupee or one lakh rupees from your pocket. The trace of sin can always be neglected. The Lord came as Bhuddha and preached this non-voilence. Veda also says that one should kill his animal nature in the sacrifice and not the animal (Manyuh Pasuh).