A valid question (with no abuse words, or intended meaning) is a valid question, No Matter who ask it or Why.
Trying to hide sensitive questions has a higher chance of causing people to lose their faith, more than a correct answer to a sensitive question could.
Why were the kings of Israel allowed to have many wives?
Could be better phrased as:
Why were the kings of Israel allowed to have multiple wives?
Did any king of Isreal have multiple wives? Yes. So please explain yourself how is this not a valid question? why is it a sensitive question? or rather, why is it a sensitive question to you? As far as christians are concerned, this is not a sensitive question but a powerful one, since the correct answer will bring us one step closer to knowing God.
If God knows everything, He should also know who is going to hell, and
no matter what happens, that person is going to hell anyway. Why does
God allow this?
Yet another powerful and valid question, but perhaps could be better rephrased as:
The Bible says that God knows everything (1 John 3:20, Job 36:4) and
nothing is ever impossible with God (Luke 1:37, Matthew 19:26).
Does that mean he knows who is going to hell?
And, no matter what happens, that person is going to hell anyway?
If so, why does God allow this?
In fact here's another example of a powerful question:
Can God create a stone so heavy that even He could not lift?
Mark 13:32 (NIV):
“But about that day or hour no one knows, not even the angels in
heaven, nor the Son, but only the Father.
If Jesus is fully God as well as fully human, then how is it that He
can be ignorant of anything, since God is omniscient or all-knowing?
Facts (truth) does not need hiding. The truth is not afraid to be revealed, because every single sensitive part of the truth is still the Truth. If not, it's no longer the truth, but merely the half-truth.
Do what we can (provide the answers to the questions) and let God do the rest.