I seem to believe that a holiday that is designed around worshipping the devil might actually revolve around actually worshipping the devil. I've never met anyone that uses, Halloween to worship any deity of any kind. People may use horrifying or demonic costumes or props to celebrate the Holiday but they're used to bring people together and promote community.
Wasn't Christmas originally a pagan holiday? I seem to remember learning that the Catholic church deemed, Christmas as the day to celebrate Christs' birthday to squash a pagan holiday.