Many Christians are absolutely uncompromising in their denunciation of Halloween and all things related to Halloween. They won't let their children dress up in Halloween costumes or go trick-or-treating. Halloween, to them, is an abomination to God - and followers of God should have nothing to do with it.
It is a matter of historical record that Halloween has its origins in pagan rituals and traditions. It is also a matter of record that the Bible condemns all forms of witchcraft. In fact, the mosaic law instructed the Israelites to execute witches. (Something that the Puritans took to heart in Salem, Massachusetts in the 1600s).
Should Christians celebrate the pagan rituals and origins of Halloween? This pastor would have to say "No." The Bible is clear that light has no fellowship with darkness and that we should not revel in sin.
Having said that...Halloween has taken on a much broader identity in today's culture than paganism and witchcraft. Many families celebrate Halloween, without giving any thought to witches, warlocks, Satanism, Druids, the occult, etc. Must they avoid celebrating Halloween with candy and trick-or-treating, because of its origins?
Bottom line....God looks at the heart. If you're celebrating Satanism, withcraft, or other forms of demonic evil, that's obviously not going to meet with God's approval. If you're just looking for some free candy, hey, I don't think God has a problem with that. So, let's take a chill pill, brothers and sisters in Christ, and not make mountains out of molehills.