What does it mean to the world that the Ghostbusters have proved the existence of life after death, and, from a moral standpoint, should they be busting ghosts at all?
These are issues addressed obliquely within the franchise itself - you may recall that Lenny, the mayor of New York City is close friends with the Roman Catholic Bishop present at the meeting between the city officials and the Ghostbusters. The Bishop says that officially, as a representative of the church he can take no stance on the events unfolding in the film. In the short term, it would appear that the church is playing the long game, waiting to see how things play out. And indeed, it seems that in the second film, after the Ghostbusters’ fall from grace and, largely speaking, from the public eye, a major theory concerning the Ghostbusters is that they are con artists rather than legitimate paranormal exterminators, using nerve gas and light shows to dupe their customers into thinking that a ghost has been present and trapped.
As for the morality of Ghostbusting, on one of the many voicemail messages you can listen to in Ghostbusters: The Videogame, a clichéd hippie voice asks the Ghostbusters to consider the ghost's feelings concerning the busting process. "That could have been somebody's Grandma," the anonymous caller accuses, "have a nice day, aggressors."
While these interactions are undoubtedly intended to be part of the joke, they do raise questions of morality and religion in the context of the franchise. If the Ghostbusters existed in the real world, they would be the impetus for changes that could have a profound effect on the entire globe. Proving the existence of malevolent spirits is bound to lend some legitimacy to the idea of Gnosticism, the idea that the world was created by an imperfect god. The essential (and apparently inherent) impurity of ectoplasmic entities suggests that there is no guarantee of your spirit reflecting your actual personality. Granted, most of the ghosts in the series are ghosts of criminals or followers of an evil demigod, but this in and of itself suggests some sort of determinism; a criminal is possessed of a "bad soul," and thus their actions in life reflect the type of soul that have. This bad soul occasional returns from the ethereal plane to shush Ray Stanz or slime Peter Venkman. Undoubtedly the old argument between determinism and free will would arise, and at some point words would be slung from one party to the other. The arguments for determinism would broadly remain the same, merely backed up by the evidence provided by the malevolent spirits in the Ghostbusters’ containment unit. Those that believe in free will would have to serious consider their structure of belief, and I feel that the only out they would have would be to describe god as imperfect. To believe in free will is to suggest that God has created ideal souls because God, by definition is an absolute ideal. Free will is an expression of that absolute power allowing us to either accept or reject recognition of that power. For those who do not believe in determinism, a perfect benevolent God would not create a malevolent soul. Thus, from the existence of malevolent spirits, it follows that a perfect benevolent god does not exist. This is not an exclusive argument, of course. There are a myriad of ways the argument could be taken. I am only attempting to enumerate one possible line of thought in the interest of suggesting the impact that proof of ghosts could have. Consider if you would the arguments you have undoubtedly already taken with what I have here proposed. Likely, they are all valid objections. The proven existence of malevolent spirits is bound to bust open the discussion on God and what nature He takes.
Thus, I humbly propose that the Ghostbusters, in the real world, could easily go by the name Gnostbusters. Not because of the links to Gnosticism I have suggested, but rather taking the word from Greek, "Gnosis," or knowledge. The Ghostbusters, through all of their ghostbusting, have simultaneously busted open the realm of knowledge of the spiritual and religious. Proof of something beyond the physical world would have wide-reaching consequence, and would no doubt be the center of much study and debate. It would be a veritable Pandora’s Box with a proton stream as a key. Some may even say it would be like the tree of knowledge of good and evil all over again - what would John Milton think? Could there be another sequel to Paradise Lost that had the Ghostbusters in it? Maybe that's too much to hope for.