Atheists in Turkey are safe but I wouldn't recommend going out into a city square touting atheism. I think a lot of people don't realize that you can live a western life in some Turkish cities without major issues. The risks come from being an activist against Erdogan.
Turkey is a secular nation with no official state religion.
Not for much longer.
(The rating on the above comment has been fluctuating wildly for that last two hours, from -1 to +3 and back.)