Even leaders in the Vatican agree that it is a barbaric and outdated practice. This is just another example of the religious fairy tale beliefs that have humanity duped into thinking any of it is real. Let alone coercing followers to buy into such harm. Priests have been convicted of homicide for performing exorcisms resulting in death! Professionally "trained" exorcist? C'mon, really? That's like saying I'm professional trained in blowing houses down that pigs live in!
Exorcism is a barbaric ritual that is rooted in the dark times of human history. As with religion in general, exorcism serves no genuine purpose and is nothing more than ritual hocus pocus that never actually solves anything. It should be banned as soon as possible for safety concerns, among other reasons.
Exorcism should be banned because there is no conclusive, or factual, way to prove that someone is 'possessed'. Possession is not a valid medical diagnostic and the illusion that performing an exorcism cleanses you of your possession can be seen as largely a placebo effect. If you want to believe that the 'evil' inside someone can be dispelled so simply, it will work in your mind, whether it has any effect or not.
More recently, many exorcisms that have gone before the court system have resulted in charges, depending on what happened to the person being exorcised. Murder charges across a family who voluntary drowned a girl in 2007 during an exorcism is just one example.
Exorcism used in the right hands of a religious leader can often drive demons out of a human. If you ban this practice, some demon possessed people will have no way of getting rid of their demons. Many times also it's a mental problem that can be healed by the placebo effect. A priest comes in and exorcises the demons out of the person, they believe and no longer act like demons are in their soul. This is a religious practice and freedom of religion is very important.
Exorcism serves an important purpose in the world: relieving those afflicted by demonic possession. The devil and all of his fallen angels exist, and they prowl about the world seeking those whom they may devour. Not just anyone can perform an exorcism of course; the Catholic Church asks those who believe they are possessed to receive extensive psychological and medical testing first to ensure they are not troubled by a more physical malady. Only then will she consent to have a professionally trained exorcist examine the patient. Even if one is an atheist and doesn't believe Christianity is not true, what is the harm that could result in an exorcism?