Ghosts and Religion

I've heard from a couple of people I know that "Christians are taught to believe that ghosts don't exist, and not to believe in mediums."
I find that all fascinating, because ghost references were scattered throughout the bible. I've looked at various websites, and the right-wing conservative interpretations of the Bible say "no." Ghosts of people who have passed don't walk the Earth. Other interpretations indicate they do. What it all comes down to is that the Bible was written by man and is not infallible, just like anything.
This is the same argument I make about pets "not going to Heaven." WRONG, WRONG, WRONG. Dogs and cats most certainly DO cross over and go to the other side. Any medium will tell you that. Any person that has had a dog or cat may be able to show signs that they've come back from the other side to indicate they're okay, just like people do. I've even SEEN my puppy that was killed standing in the light (with our 2 other family dogs who passed) when my dad walked into it in 2008. Any preacher that tells you dogs and cats don't go to heaven is lying and simply uninformed.
As for ghosts and spirits - they certainly do exist and there's a difference between them. My own aunt was stuck here on Earth as a ghost until obtaining forgiveness, then she moved on. Spirits (who have passed into the light) come back to us in our dreams among other ways. We've proven it with mediums, we've proven it with scientific equipment.
The issue I see here is that some religions have "told" people that any supernatural entity is a demon. Wrong, wrong, wrong. Yes, there are dark entities, some that are non-human, but there are genuinely ghosts and spirits that come back to communicate. Even the Vatican, who dismissed psychics and mediums now employs them. Think about it.
I found that people raised in evangelical and Baptist religions were particularly taught the all spirits were "demonic" (which is untrue). I'd like to know everyone's thoughts on this.