Although many people deny the existence of demons for various reasons, there is compelling evidence that suggests otherwise. There are really only two groups that deny the complete existence of demons these are the humanists/atheists and the feel good Jesus saves everyone Christians.
Humanism is a religion based on the fact that there is no God and no afterlife so live life to the absolute fullest as you only get one shot. Many Humanists believe that demons don't exist because they don't believe in God in the first place. For if there is no God then how can there be anything else supernatural? Humanists don't believe in God or in heaven or hell and as such they value the human experience here on earth more then anything else so they attempt to live good lives for the betterment of humanity. Some arguments that Humanists bring to the table about the existence of demons is the fact that you can't see demons, or that if there is no God and no afterlife why would there be demons.
They also argue that demons are just irrational excuses for why there is evil in the world. They argue that demons have nothing to do with the suffering and torment that is for some the earthy experience.
The worst group in my opinion is the washed up God loves everyone so everyone must be going to heaven "Christians". This group of people are Christians who have developed a very humanistic worldview. They say that God loves us too much to allow hell and without hell there is no Satan and without Satan there are no demons. These people believe that biblical accounts of Jesus casting out demons and healing people afflicted by them are embellishments to lend credence to Jesus ministry. They believe that...