Is there iniquity in my tongue? - This is a solemn appeal to their consciences, and their own deep conviction that he was sincere. Iniquity in the tongue means falsehood, deceit, hypocrisy - that which would be expressed by the tongue.

Cannot my taste discern perverse things? - Margin, palate. The word used here חך chêk means properly the palate, together with the corresponding lower part of the mouth, the inside mouth. Gesenius. Hence, it means the organ of taste, residing in the mouth. The meaning is, that Job was qualified to discern what was true or false, sincere or hypocritical, just or unjust, in the same manner as the palate is fitted to discern the qualities of objects, whether bitter or sweet, pleasant or unpleasant, wholesome or unwholesome. His object is to invite attention to what he had to state on the subject. To this proposed vindication he proceeds in the following chapter, showing the greatness of his calamity, and his right, as he supposes, to complain. Their attention was gained. They did not refuse to listen to him, and he proceeds to a fuller statement of his calamity, and of the reasons why he had allowed himself to use the language of complaint. They listened without interruption until he was done, and then replied in tones of deeper severity still.

Job 6:30 Parallel Commentaries

The Sinner Stripped of his Vain Pleas.
1, 2. The vanity of those pleas which sinners may secretly confide in, is so apparent that they will be ashamed at last to mention them before God.--3. Such as, that they descended from pious us parents.--4. That they had attended to the speculative part of religion.--5. That they had entertained sound notion..--6, 7. That they had expressed a zealous regard to religion, and attended the outward forms of worship with those they apprehended the purest churches.--8. That they had been free from gross …
Philip Doddridge—The Rise and Progress of Religion in the Soul