Ask him these questions:

1. Where is the segmented blue circle on the sectional that signifies Class D*?
2. Why doesn't it mention the Class D status in the AFD?
3. Check out FAR 71.61 and the Order it references**.
4. Give me a reference to one official publication or recognized aviation author who agrees with you.


...or you could just chalk it up to having one of "those" instructors.

* as I recall, there are a few: Class C that reverts to Class D dues to part-time Class C status. You can also compare it to the various TRSAs that are still around - they will show the Class D segmented circle.

**btw, he's probably using as his reference the "general" definition of Class D that appears in the AIM. The official one is in Part 71 and the Order referenced is a list of all Class C and D airspace.