The truth is what is. And what is, is all around us, and is even in us. If I want to know the truth, all I have to do is recognize what's in and all around me. I need no "authorities" to recognize the truth for me, and neither does anyone else.
But there's a really big wrench in the works, here. And that wrench is our natural human desire to deny the truth of what is in favor of illusions of truth that make us feel better.
The truth about God is all around us, and is plain to see to anyone who is willing to look. The truth is that we simply do not know. Our definition of "God" is such that we cannot possibly verify the nature or existence of such an omnipotent, omniscient, omnipresent force. How can a finite being such as ourselves possibly verify the nature or existence of an infinite phenomena? What tools could we use? The answer is none. We don't have any tools to verify such a concept, and so to us, "God" remains an unverified concept. That doesn't mean that God does not exist. It does mean, however, that we can't know if God exists or not. And if we can't know if God exists, we can't know God's character or nature, either.
And convincing ourselves that God exists (or that God does not exist), by practicing self-deception, does not change the truth of what is: the truth that we simply do not know.
So if I meet a man who claims to speak for God, I know he's a liar and a fool. He's not a liar because he can't possibly speak for God, maybe he can, we don't know. He's a liar because I know that he can't know whether he speaks for God or not. As a human being, he doesn't possess the tools necessary to verify such a claim. And he's a fool, because he has fallen for his own lie. He has deceived himself.
But we humans are often liars and fools. It's in our nature to deceive ourselves into denying the truth of 'what is' in favor of imagined "truths" that make us feel better. So I'm not trying to humiliate people for fooling themselves into believing that they "know God". I, knowing full well that I cannot verify the existence or nature of "God", still choose to believe that God exists, and that the essential nature of God is love, even though I can't verify it. So in a way, I'm a willing fool, too, along with so many other human beings.
But I'm trying not to be a liar. I'm not claiming that I know that God exists, or that I know God's nature. And I'm not afraid to reject that claim by anyone else. I'm convinced that such self-deception is the root cause of much human suffering, and I would prefer not to support or promote it if I can help it.