Below are few Biological, Historical, Geographical and Religious reason why non veg food is allowed…

1) Living beings are divided in to 3 categories – Herbivorous, Carnivorous and Omnivorous.

Herbivorous animals like cow, horse, elephants etc…are designed in such way that they can digest only veg food.

Carnivorous animals like tiger, lion. Hyenas etc are designed in such a way that they can only digest non veg food.

Omnivorous like we human beings are designed in such a way that we can digest both veg and non veg food.

2) If we look at design structure of teeth, Herbivorous animals have molarl teeth to chew veg food, Carnivorous animals have incisor teeth to tear the flesh, and we human beings have both molar and incisor teeth.

Above 2 points clearly confirms that biologically we are designed to eat both veg and non veg food.

3) Human civilization is 5000+ years old, and early humans use to rely on hunting animals to survive as there was no vegetation.

4) Geographically if we look at cold countries like Greenland,  Iceland,  Ireland few places in Russia and Island countries, there is few or no vegetation, and they have to rely on Fish and other sea foods to survive.

5) Also all religion which has concept of God, allows eating non veg food, like Islam, Christianity, Judaism. Parsism and Hinduism.

Religions like Buddhism and Jainism do not allow non veg food as these religions do not believe in concept of God.

6) Scientific research has shown that even plants have life as they also grow, they need water, they need food in the form of photosynthesis and they also die.

7) There are 100 Crore Hindus in India, and out of which 80% are non vegetarians…which means 80 Crore Hindus eat non veg., and only 20% are vegetarians may be because they are influenced by Buddhism or Jainism instead of their own religion Hinduism.

8) In few Hindu temples priest sacrifice animals like Goat or buffaloes as tradition and custom to please their God and Goddess.

In Nepal during their festival Gadhimai, 5000 buffaloes are sacrifices as rituals.

9) Aghori sadhus eat human flesh, which is flesh of corpses brought to the cremation grounds.

10) In animal Zoo, where Carnivorous animals are kept like Lion, Tiger, Hyenas etc. are given non veg food to keep them alive even by vegetarians.

11) Many deadly disease like Dengue, Malaria etc are caused by Mosquito, and we use spray to kill them which is necessary to keep humans safe..

12) Even farmers to protect their crops use pesticides to save their farms.

All above points confirms non veg is allowed by God, and sometimes we have to kill deadly animals and insects to keep humans safe and necessary for survival of humans.

Eating non veg food is not compulsory in Isalam, and a person can be a Muslim even if he is vegetarian.