The evil spirits that correspond to the Assyrians are those who would use our rational minds to pervert the doctrines drawn from the Word into false ideas. Unlike the Moabite-like spirits, who attempt to lead into falsity from our experiences in the world through our senses, The Assyrian-like spirits attempt to look like pious and learned scholars of the Word, shunning worldly interests. But inwardly they are using the literal sense of the Lord's Word to justify falsity and evil.
Our defense lies with the internal sense of the Word. The king of Israel orders his soldiers not to answer the blaspheming words of Sennacherib, King of Assyria. Likewise, the Lord would have us not use our rational minds to justify or argue for or against the higher teachings of the Word. Instead, we are called to first listen to the voice of the Lord in His Word as it really is, and then to use our rational minds to confirm those teachings from the literal sense of the Word.