One of my twin sons was afraid to go in the Haunted Mansion his first time. Not terrified, just apprehensive.
He was probably six or seven years old at the time.
Now, as his father - I obviously knew him well, and knew what scared him. I knew the HM well too, and knew that what scared him - really scared him, not temporarily gave him a jolt - wasn't contained in the HM.
I was very big on age appropriate things and would not have brought my son into a graphic blood and guts display.
That's the kind of thing that scared him, and that's the kind of thing I would not have subjected him to at that age.
(Speaking of which, many neighborhood Halloween decorations have entered that realm.)
I really wanted him to go in HM, because again - I knew what was in there, and that my son would not only be fine with it, but that he'd actually enjoy the whole experience.
"Disney Scary" I told him.
"Disney doesn't do the type of things that you are afraid of, and you know that daddy would never do that to you..."
Anyway, we went in and he thoroughly enjoyed it, of course.
The rest is history as they say.
Oh!
Side note...
On the Jungle Cruise (same trip) as the boat turned around to reveal the blowgun and spear holding headhunters, my son ducked!
Hysterical, and one of my favorite WDW memories!!
Let's hope no one complains about the headhunters.