“I would suggest that it is impossible for man NOT to insult God.”
We are defining a term down. It is impossible for a believer to treat God contemptuously or rudely. They are intentional actions of insolence. The Holy Spirit would not allow that. We may be angry with God or upset with Him but not contemptuous. We may have lapses of faith or doubt but not to treat God with insolence. That attitude belies belief in or the knowledge of God.
The unbeliever can’t insult God for there is no relationship in which to address God or treat Him with indifference. They are dead.
It is probably impossible to insult God. One would have to have such standing with God that such a thing would be possible. God is so far above us that He cannot be insulted by us.
On the other hand, humans can TRY to insult God. God gets hacked off at the effort because it’s insolent and disrespectful.