God has the right to do WHATEVER He pleases.
If I’ve learned one thing from studying hell, it’s that last line. And whether or not you end up agreeing with everything I say about hell, you must agree with Psalm 115:3. Because at the end of the day, our feelings and wants and heartaches and desires are not ultimate — only God is ultimate. God tells us plainly that His ways and thoughts are infinitely higher than ours (Isa. 55:9). Expect then, that Scripture will say things that don’t agree with your natural way of thinking.
— Francis Chan, Erasing Hell, p. 17
Josiah Concept Ministries 
“you must agree with Psalm 115:3”
Why must I do this?
You are not the target audience of that quote — people who already accept the Bible as the Word of God. The target audience would not ask that question.
That Psalm is part of the Bible, which we Christians believe to be the inspired words of God. Therefore, we would agree with Psalm 115:3. You, the skeptic, will not.
But that’s a different conversation.