Personally, I try to look at what the bible actually says, that way, if you are a Christian you get to see what God actually thinks. That approach made sense to me anyway.
Two texts that sum it up,
Deuteronomy 18:10-12
^10 There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch,
11 Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer.
12 For all that do these things are an abomination unto the LORD: and because of these abominations the LORD thy God doth drive them out from before thee.^
and
1 Corinthians 10:20, 21
^20 But I say, that the things which the Gentiles sacrifice, they sacrifice to devils, and not to God: and I would not that ye should have fellowship with devils.
21 Ye cannot drink the cup of the Lord, and the cup of devils: ye cannot be partakers of the Lord’s table, and of the table of devils.^
So for me personally, I find it quite clear that both the Old & New Testament show God hates anything to do with the occult, spiritism etc, using words like 'abomination', so pretty strong stuff. Even if I don't worship the devil, I don't think dressing up as him is going to go down well! :)