One cannot adhere to a DOGMA (any dogma, not JUST religious dogma) and be a free thinker.
One can BELIEVE something of course, but if one believes that something without question, if one clings to a belief even when evidence comes to light that makes that dogma dubious?
Then one is not a free thinker.
A LOT of people who are atheists are not REMOTELY free thinkers.
They believe other dogmas which cannot be proven, which means that they are not exactly the free thinkers they might like to think they are.
I used to think that way. Then I became Born Again, and realized God needs us who believe in Him to be Free Thinkers. We SHOULD question with boldness even the very nature of God, but remember that God is not a man that He may be shown a liar. God did not give us this incredible intellect to be just robots. He did not give us free will in which to follow blindly.
You must understand the nature and goal of God is to have us love Him. You can't have love without free will and the choice to hate Him. Without that choice, what can you do but follow the inevitable truth of His existence as your creator.
So when you choose to hate God, it is your choice freely given, and much to His grief.
There are certain undeniable truths to the universe, and He and his Law, as well as Grace are some of them. Just like gravity, matter and energy. This is just one of them. No matter how free thinking you are, you would not deny that matter, energy or gravity exists. Well you could, but that would not stop you from dying by a bus hitting you, falling out a window or having a million volts run through you. It's the dangers of an objective reality, nothing more
But go ahead and free think all you want. Your perspective is not shared nor objective. Then again... neither is mine. Makes it really complex, doesn't it?