“In conditioned life, all work is contaminated by the material modes of nature. Even if one is a brahmana, he has to perform sacrifices in which animal killing is necessary. Similarly, a kshatriya, however pious he may be, has to fight enemies. He cannot avoid it. Similarly, a merchant, however pious he may be, must sometimes hide his profit to stay in business, or he may sometimes have to do business on the black market. These things are necessary; one cannot avoid them.” (Shrila Prabhupada, Bhagavad-gita, 18.48 Purport)