some people may not eat meat thus vegrtarianism best for every one at all times
That is true 
some af the religious people that originated from an ancient people may think eating meat is against their rules 
You are correct. They are also called vegans
Milk and meat in Jewish law
Mixtures of milk and meat (, "basar bechalav", literally "meat in milk") are forbidden according to "Jewish law". This dietary law, basic to kashrut, is based on two verses in the Book of Exodus, which forbid "boiling a (kid) goat in its mother's milk" and a third repetition of this prohibition in Deuteronomy.
According to the Talmud, these three almost identical references are the basis for three distinct dietary laws:
Ethics of eating meat
The question of whether it is right to eat animal flesh is among the most prominent topics in food ethics. People choose not to eat meat for various reasons such as concern for animal welfare, the environmental impact of meat production ("environmental vegetarianism"), and health considerations. Some argue that slaughtering animals solely because people enjoy the taste of meat is morally wrong or unjustifiable. Vegans often abstain from other animal products for similar reasons.
Ethical vegetarians and ethical vegans may also object to the