Evil is a term used to de-humanise individuals. The term implies monstrous bad behaviour.
Evil is the opposite of Good. A Bad Thing is not Good, but can generally be tolerated. An Evil Thing, on the other hand, is something that goes directly and deliberately against the grain of what many would consider ethically correct.
Many centuries ago, when the printing press was spreading, church leaders condemed the machine as evil because of the fear that unmoderated ideas would break down society. For example, unauthorized biblical translations. Similar voices echoed this sentiment at the arrival of the telegraph and the telephone.