Therefore, killing any soft natured animal or any soft natured human being is a sin provided it does not attack your life. Except this one point, you should not kill any human being or any soft natured zoological living being. All other reasons can be enquired by law and corresponding justified punishments other than death sentence should be given. Hence, cow slaughter is only a part of the total concept and this part should not be emphasized as the total concept. You try to extend this partial concept to the other similar items also and arrive at the general total concept. Taking the advantage of the slaughter of other soft animals, you should not kill the cow.
The fundamental cellular fluid in Botany is cytoplasm whereas the fundamental cellular fluid in Zoology is protoplasm. The neuro spot giving awareness exists even in unicellular organisms (Amoeba) of Zoology. If you justify killing of animals for the sake of food, you have to simultaneously justify the killing of human beings for food by demon or present carnivorous human beings present in the forest. Kaapaalikas eating the dead bodies of human beings are justified. Proteins primarily synthesized in plants are good for health whereas proteins re-synthesized in flesh are not good for health. Bhagavan Shri Satya Sai Baba even as a boy used to become curious if a bull of cart was beaten. The highest justice is non-violence (Ahimsa paramo dharmah…). If you say that you will kill the animal by giving anesthesia, it is also not justified because you have no right to take away the God given life from its enjoyment. Will you justify your killing also by the demon if anesthesia is given to you? In such case, even an atheist will argue such human killing is unjust!
Shri Ramakrishna Paramahamsa was found killing blood (bed) bugs in His cot. The blood (bed) bug or a mosquito can be killed harming you seriously. But, non-harming ant or butterfly etc., should not be killed. Bhagavan Shri Shirdi Saibaba showed the wound on His body when a devotee beat a buffalo. By this, He is preaching that human being doing violence should keep in the place of victim and imagine the suffering of the violence. Can He be a non-vegetarian as some people criticize? Buddha left this family life on seeing when a swan was shot. In the Valmiki Ramayanam, an inserted incident was told that Rama killed a deer in Panchavati forest. He killed certainly the golden deer since He knows it as a demon in disguise. Rama was never a non-vegetarian as spoken in the Valmiki Ramayana itself (Na maamsam Raghavo Bhunkte…). Even Jesus, the embodiment of love, was not a non-vegetarian and reports otherwise are false, which were created by the non-vegetarian followers only. Mahavir preached extreme non-violence by restricting the justified non-violence also so that people will not do atleast the justified non-violence. Here, (n+1) rule applies, which is to preach the highest goal so that atleast high and higher goals are achieved by the followers.
Non-violence is the fundamental justice and no divine scripture in the world can preach atleast the justified non-violence. Scriptures are polluted by the insertions done by the followers and hence, logical analysis is the ultimate filter to reject such insertions. Sometimes the human incarnation may not oppose such fundamental non-violence also since it is strongly established. The human incarnation may neglect even such fundamental issue in view of concentration on other issues so that when other issues are rectified, this fundamental issue can be taken by next human incarnation in course of time. Such fundamental strong issue is dealt by partial controls step by step. The scripture says that fish should not be captured on holy days in holy places. This is a partial control in the initial stage. Finally, the scripture preaches the step called as ‘Mahavratam’, which is not to catch the fish in any place on any day. Full and permanent reformation on any issue can come only through the divine scriptural knowledge. Enforcement through rules can bring only partial and temporary control.