This one is fairly easy. It is a matter of the claims, and the evidence. With spirits, people from all over the world in many eras, and across many religions, all claim to have seen or otherwise interacted with spirits of the dead. Their claims are that these beings are insubstantial, and visit with only specific persons.
Finding evidence of insubstantial entities, who only visit specific persons, at random times is difficult to prove or deny. PLEASE NOTE that many claims about spirits moving things around the room, or taking actions here in the physical world, have been thoroughly refuted.
Add onto this, the cultural mores of smacking down the depressed and grieving family members of the recently deceased who often make these claims
, and you could see how this subject is treated with kids gloves, even in the scientific community.
However, in the case of young earth creationists (YECs)….they have stated that the mountains and the rocks, and all life, and the oceans, etc….are all roughly 7000 years old.
This is undeniable bull-hockey, since many many many studies can be, and have been, run to judge whether this relatively precise claim in the physical real world is true or not. Every study done has shown that the claim is absolutely false. Also, only a small subset of Christians (as far as I know) have made this absurd and repeatedly disapproven claim.
So, Mock Away!