As did Skinner, Watson had been conducting behavior modifica

To put the problem with A/C/E succinctly, you don't want to compare "did" & "had" here. Let's look at a different example:

As I did, my father had majored in English in college.

At first glance, this might seem fine. We have two events: I majored in English, and earlier on, my father majored in English. One objection, however, is that there is no clear event that "had majored" precedes. Sure, we can figure that my father attended college before I did, but we generally want a clear, explicit reference to justify past perfect. ("He had majored in English before the department experienced its decline.") Anyway, this might not seem like a big problem in my example, but it's certainly a problem in the original. How do we know Watson's work preceded Skinner's? If anything, it appears that they both were forced to stop at the same time.

In any case, there's another problem. Even if one event did precede the other (yes, my dad really did go to college before I did), that doesn't necessarily mean that we should use the past perfect. What if I said "I have been to Spain and France"? One of those trips must have preceded the other (unless I hiked the border!), so should I use the past perfect? No! Not unless I definitely want to stress the order of the trips--"I had already traveled extensively in Spain when I visited France, so I felt prepared for my return to Europe." Let's rewrite my example:

As I did, my father majored in English in college.

This is better! Both events happened in the past, but the point of the sentence is to point out a similarity between them, not to show how one preceded the other.

"But wait a minute!" you say. "The past perfect isn't there to compare Watson to Skinner. It's there to show how Watson did this work before people questioned the ethics of it!" Yeah, that might work, except . . . why is Skinner in the simple past, then? This gets us back to the beginning--we're making a comparison between what two people did. They both did some work until it was questioned. Why put one in the simple past and the other in past perfect? No reason! Cut A/D/E.

Okay, maybe I spoke too soon when I used the word "succinct," but I hope folks find this helpful.