Nothing is safe if you are depressed, nervous or suffer from any form of mental illness. That applies to established religions as well. If you are delusional, it makes no difference whether the voice in your head is from God or the Devil.
We played with an Ouija board years ago and, frankly, it was hilarious. The replies we got were often very rude and always silly - sometimes we laughed so much, we could barely hold on to the glass. It has nothing to do with genuine spirituality, of course, nor is it used in the Spiritualist church.
In our case, all the people playing with the board were either atheists or, like myself, Pagan. Atheists, of course, don't believe in the Devil and Pagans don't either. You're less likely to be scared of something you don't believe in. Basically, it's just a silly, but sometimes funny, game with an exaggerated reputation. It's only dangerous to people who are highly susceptible.