Psychological and social motivations and implications of activities are important. All actions start in the mind. Evil deeds are caused by ignorance and selfishness. If the ego is allowed to grow, it generates anger, greed, lust, hatred, etc. and makes life miserable for all. They should be offered in fire.
Mental environment has to be kept clean and focused.
Yajna is the sacrificing of one's ego and the burning of impurities. When it is accomplished, one's society and environment are purified. Whenever worship-service is performed in the Hindu tradition, it is preceded by purification of elements, 'bhutasuddhi' as a necessary preliminary. The five elements are purified both within and without. Only when these elements are pure or purified, can they be offered in worship.