There are sects of people who believe that Halloween is a satanic or devil worshiping religion. On the other hand I think Disney/HP is mostly viewed as fantasy storytelling.
Tell that to my cousin. Her mother absolutely forbid her from reading HP or watching the movies, because her fringe religion preached that merely reading the spells would conjure the devil. On the other hand, she happily put my cousin on a plane at age 12 to spend a week with me at
HHN, and she got a kick out of all the photos.
I'm coming at this from a very different perspective than most. My dad's family is Jewish. My mom's family is conservative Christian. And my mom's family's church hosted an elaborate Halloween party every year, complete with full decorations and costumes. We like holidays, and we celebrate almost everything.
In addition, for a variety of reasons I went through a series of private Christian schools as a kid. Halloween decorations are not indoctrination. Being forced to spend a week at a "camp" that was actually a religious revival, force marched to a tent meeting in front of a bonfire at 2am, and repeatedly told that your parents are trying to drag you down to Hell because they aren't part of the school's religious sect? That's indoctrination. I was all of 8 years old at the time. Indoctrination can also take the form of forcing kids to write essays on why the Salem Witch Trials were a GOOD thing (yep, that happened too) and similar such assignments.
For high school, I ended up in a rigorous college-prep school that happened to be affiliated with the Episcopal church. My first year I took a required World Religions course. The first day, the teacher brought in copies of all the major religious texts--the Bible, the Quran, the Book of Mormon, etc. He set them all on the desk and asked a simple question, "Which one is right?" After some discussion, he explained that they're all right, and they're all wrong, because they all contain something that is valuable to someone, but none of them have the complete answer to anything. It was mind-blowing to me after years at those other schools.
What I've come around to is this: Religious/spiritual belief is an incredibly personal thing. Two people in the same exact church don't necessarily hold the same exact beliefs. And the same person can hold conflicting beliefs, like my Grandma. She was very anti-gambling. When a group of us went to the casino during a family reunion, she lectured us up and down. When we came back and told her we hit the jackpot, she fell to her knees praising the Lord. And when we said we were just kidding, she went right back to talking about the sins of gambling.
So yes, we could remove all traces of any holiday from the classroom environment. It would be "equitable," but so very boring. We could create generic winter parties and fall festivals, but that would take away some of the magic. Or we could strive to be as inclusive as possible, and use the holidays as teaching moments to explain different world views--which I believe would be incredibly valuable. Individual parents could opt their kids out, but everyone else would learn valuable lessons that would serve them for a lifetime.