Villians, in the moral context of this play, are those who 1) know that witchcraft is not going on in Salem, 2) understand that the implications of their actions, attitudes and claims and 3) consciously choose to follow through with those claims, attitudes and actions while watching others suffer for it.
The conflict in this play is caused by fear. People in the town fear the girls, they fear being outcasts. Survival in this type of close-knit and isolated community is absolutely dependent upon being accepted by your neighbors. Once that acceptance becomes fragile and uncertain, fear fills the community and they will look to anyone or anything to help alleviate that fear.
This is where the heroes and villians enter. Think of times in this country where fear has been rampant - the terrorist attacks on 9/11, for example. In that time, people clung to the idea of heroes - soldiers and firefighters and the like - for a feeling of safety. They also firmly identified villians, as an outlet for anger and grief. This is natural. In The Crucible, the town has its villians - anyone suspected of anything out of the ordinary, anyone identified by the girls. Heroes, however, are harder to come by. Abigail is too unstable to be a hero that people look to. John Proctor does behave heroically, but it is mixed up with his own character flaws, and he does not inspire confidence in the townspeople. Reverend Hale shines as a hero to the town, welcomed in by them to look over the girls, and honored when he "discovers" the truth. What is ironic is that Hale is not behavingly heroically - he is naive and misled by his own beliefs, as he later realizes. But to the town, he is a knight in shining armor.