To be completely honest with you, I find this sort of thing very frustrating. This is just one more example of Muslims applying a completely biased approach. These people do not read the Word of God in order to learn what God has to say to them. They simply read it in an insincere and sometimes downright dishonest attempt to find dirt of the holy Scriptures. Do they have nothing better to do than to try to use biased and unfair criticism to try to destroy the faith of Christians? I suggest that they should read their own Scripture to make similar criticisms. There is plenty there to criticize. But let me talk about these three cases since you asked.
First of all, in Isaiah 20:2, Isaiah is not being asked to go about stark naked. Just read the passage. God said to Isaiah, “Take off the sackcloth from your body and the sandals from your feet.” If you or I take off our outer garment and go barefoot, we will still be wearing an inner garment. I am fairly sure such was the case with Isaiah. We know that when they took the outer garment off of Jesus, he had an inner garment on. That is the one they gambled over. Jesus was truly naked on the cross, but Isaiah was not.
Besides, how is a Muslim to decide what God can ask his prophet to do? What if God did ask Isaiah to go naked? He did not, but what if he did? The problem in this case was the sin of idolatry of the people. If God asked Isaiah to go completely naked (he did not) in order to get the attention of sinful Israel, who is man to tell God he cannot do that? The fact is that later, when Samaria was taken into captivity, they did so “with buttocks bared.” God will do anything to help his people not be destroyed or taken into captivity. In this case, God is using his prophet Isaiah to warn his people against the sin and the consequences of that sin. I do not agree that Isaiah was completely naked, but even if he were, if God chooses such a shocking means to get the attention of his people about a coming tragedy, that is up to God.
In Ezekiel 16 and 23 there is some truly shocking language. That is for sure. God hates sin. God REALLY hates sin. He saw the sin of Israel as truly disgusting. The sin of Judah was going to cause them to be utterly destroyed. Their sin was an utter abomination. If these Muslims want to fault God for using such strong imagery to get the attention of his people, that is their priviledge, I suppose, but I personally will not have the audacity to question God on this. This is the God of the universe who is trying to get the attention of an unfaithful people. If he uses strong imagery to do this, I say good!
The answer is yes. I have taught Ezekiel 16 and Ezekiel 23. I warn my audience that the language will be very strong, but then I read these passages. This is the inspired Word of God, and I do not hesitate to read it to Christian believers because God REALLY hates sin.
On Nahum 3:5, Again, God is rebuking people for their stubborn sinfulness. In this case, it is the brutal Ninevites that he is criticizing. These are a violent and idolatrous people. He is describing, not what he would do to his people, but what their enemies would do to them. These things really did happen when God allowed Nineveh to be destroyed by the Babylonians. What is wrong with God warning the Assyrians/Ninevites about the wrath that is coming on them?
Like I said, this is simply Muslims reading the Bible, not to learn about God, but looking for a reason to unfairly criticize the inspired Word of God. God will have a word with them at the end of times.