OK - honestly, saying the Ouija board is "evil", is like a mechanic saying a Porter Cable impact wrench is evil because one once slipped and he/she busted their hand.
Like a pendulum, a Tarot deck, divining rods, and other items, it's a tool. Like any tool, be it a Ouija board, tarot deck, air-impact wrench - any tool - can be harmful if used improperly. In fact, I can say more a nail gun is far more dangerous than a Ouija board.
The idea is to use them safely, with high vibrations. The psychic equivalent of safety glasses and gloves.