Yes, we can be brutally honest with God. But wait.

Don't move too fast. It doesn't turn out well for everyone.

Brutal honesty is not in and of itself a virtue. You can be brutally honest and, at the same time, a torturer, murderer, abuser, or racist. Yes, a person can be brutally honest and unrepentantly evil. 

It seems God may be looking for something more than brutal honesty from us. 

When the Psalmists are brutally honest with God, God not only seems to accept it, he canonizes it. Their complaints become our very prayers as we pray the Psalms. 

Our prayers then accuse God, "You have disgraced us, abandoned us, and forgotten us." 

You have rejected us and disgraced us. (Psalm 44:9)

Our prayers taunt God, "Wake up! You have obviously fallen asleep." 

Awake! Why are you sleeping, O Lord?
    Rouse yourself! Do not reject us forever! (Psalm 44:23)

These are the prayers God has given us to pray. 

But when the Israelites complain about the meal God prepared for them, he sends poisonous snakes.

And the people became impatient on the way. And the people spoke against God and against Moses, “Why have you brought us up out of Egypt to die in the wilderness? For there is no food and no water, and we loathe this worthless food.” Then the Lord sent fiery serpents among the people, and they bit the people, so that many people of Israel died. (Numbers 21:4-6)

What's the difference? There are no hard and fast rules on this. But here are some thoughts. These thoughts are not separate options that could stand on their own. They are meant to be one.

Don't take being brutally honest with God lightly and don't take it for granted. He is the Almighty and holy. The Psalmists don't presume; they appeal to God's own promises, to his covenant, to his own word. 

The complaints in the wilderness are cries of spoiled discontent; the complaints in the Psalms are cries of spiritual disorientation. Given God's promises (or, at least, their understanding of those promises), the Psalmist is having trouble matching their experience with God's own promises to his covenant people. 

And those prayers of complaint and taunting are usually resolved in praise. In those prayers the content of the praise often voices God's answers to our disorientation, although his answers are rarely simple or lacking in mystery. 

One more thing. God seems to tolerate complaining better when we do it to his face. The Psalmists address God directly in prayer. The wilderness Israelites complain about God, but they don't complain to God. So one speaks to God to whom they relate personally. The other speaks to God as consumers entitled to good service. 

Fear God, but don't be afraid to be brutally honest with him.

Unless, of course, you have good reason to be afraid.