Religions, even those that are radically monotheistic, do not necessarily deny the existence of other gods or spiritual beings. On the contrary, they claim other gods are not worthy of worship and in actuality are demons who mislead followers from proper belief or practice. Christian missionaries often employed demonization tactics when converting pagans, although Judaism, Islam, and other religions have similar histories. Demonization is not limited to focusing on other religions but can also be directed inward to condemn various schools of thought or movements.
From a secular viewpoint, demonization can be used to denigrate an opposed individual or group, making adherents to your own religion or viewpoint less inclined to do business with them (and possibly convert) and more inclined to fight against them. If foreigners are evil and corrupted by demonic influence, then any means of self-defense is easily portrayed as legitimate. The portrayal of almost all pagans in the Middle East as Baal-worshippers in the Hebrew Bible is an example of this. If pagans are corrupted by the demon-"god" Baal, then clearly they must be fought or at least oppressed. Especially in the earlier books of the Hebrew Bible, foreign deities are portrayed as existing and corrupting entities rather than being mere powerless idols. Some would argue this later transferred to Christianity after Constantine I's ascension in its suppression of Roman paganism. Some of the most known of these demonizations are Lucifer, Beelzebub and Baphomet up to the extend that they became synonym for the devil/satan of Abrahamic religions. Later, the language of demonization would be invoked during the Spanish Inquisition, leading to the expulsion of Jews and Moriscos from Spain.
The view of early Judaism treating foreign deities as devils and later Judaism treating them as non-existent is not universal. Psalms 96:5, for example, is alternately translated as, "For all the Gods of the gentiles are nothing," "For all the Gods of the gentiles are devils" (Vulgate), and "For all the gods of the peoples are idols."(NRSV) The Greek Septuagint translation of that passage, used by the early Christian Church, used the "devils" version. Jerome would follow the Greek text rather than the Hebrew when he translated the Latin Vulgate edition of the Bible. The "devils" epithet would still appear in Bibles up until the end of the 20th century when the consensus reverted to the original Hebrew text for modern translations.
Analogs to demonization exist outside monotheistic religions, as well. Polytheism easily accepts foreign gods in general, and in times of conflict, a foreign nation's gods would sometimes be portrayed as evil. Less commonly, it would be applied to other religions as well. For example, Buddha's portrayal in Hinduism varies: Some strains of Hinduism consider the Buddha an incarnation of Vishnu while in some texts such as the Puranas, he is portrayed as an avatar born to mislead those who deny the Vedic knowledge.[note 1]
In a certain way, the demonization had sometimes a positive side. For example, during Catholic missions in South America, the demonization of indigenous beliefs or acts make those peoples be regarded as so human as the Europeans.
Demonization is sometimes used against what are arguably political opponents rather than religious ones. The Knights Templar were destroyed by accusations that they worshipped Baphomet from King Philip the Fair. Baphomet, often thought to be Beelzebub, may have been used because of the likeness of this horned deity with the Christian images of Satan.