The ideomotor effect has been recognized since it was named 1852 by the scientist William Benjamin Carpenter. Faraday conducted some of the early experiments, and it has been proven over and over again in experiments and studies.
Knowledge of the phenomenon has led to "spiritualists" and "mentalists" using it to their advantage. Knowing it exists makes one much less able to be taken in by those people who want to convince you of their alleged powers.
So, if you have an issue with it, take it up with science.
It still doesn't make the Ouija board a good idea. Wanting to engage evil is a very bad idea.
Why would you present what appears to be a scientific explanation for movement of the Ouija board, but then turn around and warn people not to mess around with evil?