Question: Why have the Ulamah (learned) declared that alcoholic drinks are najis, whereas it cleans many things from the effects of contagious disease and kills many bacteria then what is the reason of it being impure?
Answer: Basically those things in Islam which are declared as najis have different reasons:
From them some are najis due to their ingredients and because of them many disease take place (for example Urine and Blood) that is why Islam has considered them najis and instructed to refrain from them.
In the other sphere come those things, which are not apparently bad but are inertly bad and that is why Islam has stated them to be impure. For e.g. infidels - it is possible that a Kafir may be clean and tidy, as it is told in the answer of the seventeenth question that they are deviated according to faith; that is why he is impure on a spiritual basis, which cannot be removed by apparent cleanliness.
To safeguard the beliefs of Muslims, Islam has stated the infidels to be impure, that Muslims can be stopped from intermingling with them and save their spiritual cleanliness. If the infidels were not considered impure and it was allowed to intermingle with them it was possible that many people who do not have strong faith would have been impressed from their sayings and thinking.1
Free intermingling with infidels would result in their penetrating into Islamic societies so restricting intercourse with them would protect the Muslims from any possible danger from them.
Thirdly are those things in which the above impurity is not there, but they are source to many social and personal problems for e.g. the alcoholic drinks.
It is correct that alcoholic drinks clean the contagious effect, but alcoholic drinks cause many evils. To stop those evils Islam has declared it impure. People would thus remain away from it, because it is natural that by not using something made from alcohol will creates hate towards it and this itself is war against alcoholic drinks.2