This stems somewhat from a previous point, and is illustrated beautifully by reference to some of the same material. Even if one allows that Doherty has employed C K Barrett fairly, as per the previous discussion, one cannot help but get the sense that he has not read Barrett through in any event. So if he hasn't quote mined, he has prooftexted.
To see this in action, one need only look at the real core of Doherty's argument, the Argument from Silence. Doherty's argument is, in essence, that if there are occasions where we should reasonably expect a source to mention knowledge of historical (or alleged historical) events, and the author does not mention them, the author therefore does not have knowledge of them.
The reasoning here is perfectly sound, and employed in historical crit. all the time. Thus, for example, that Paul doesn't mention Peter's denial, when surely he would have benefitted from doing so, means he probably never heard of it.
But where we start running into problems is when it is questionable whether or not that expectation is justified. Many of Doherty's objections to standard readings of the epistolary record rely on Paul's term "gospel," and what he meant by it. To Doherty, "gospel" is Paul's "knowledge of the Christ," at least in most instances, and he bases his argument from silence on the notion that Paul's gospel concerns past events.
Which brings us back to the top. Because if he was engaging Barrett, he'd know that Paul's gospel isn't his "knowledge of the Christ," at least not all of the time (1 Cor 15 stands out as such an exception to this, which we'll discuss in more detail in the 1Cor series I promised a short while ago), and it in fact has Doherty's connotation at best only rarely (to be fair, Barrett would not agree with me. That's okay, we won't tell him. He would agree with me enough to make the point here). At the very least, Barrett and I would agree that Paul's gospel has as much or more to do with present reality than past events, mythic or otherwise. It reflects an existing opportunity more than how that opportunity came to be, except in broad strokes.
Thus, for example:
It is the message of salvation he is commissioned to preach, the announcement of the manifestation of God’s righteousness (see vv. 16 f.). Behind this usage, lies not only the common Greek meaning of the word but also its use in the Old Testament, especially in Isaiah where it (and particularly the cognate verb) points to the coming of God whose saving righteousness will bring deliverance to his people (e.g. Isa. 40:9; 52:7).
C. K. Barrett, Black's New Testament Commentary: The Epistle to the Romans (Rev. ed.; Peabody, MA: Hendrickson Publishers, 1991), 19.
The new, good news is that now, in the present age, God’s righteousness has been manifested apart from the law.
ibid, p69 (emphasis original, citing Rom.3.21)
Romans 1.2, the verse Barrett is discussing, in fact makes an appearance just outside Doherty's top 20 silences (He suggests it should be next in line, so we can call it #21, I suppose), but is largely there because Earl doesn't know what Paul's "gospel" in this verse is, or, if he does know, he's not telling us how he gets there, and why he gets there in the face of exegesis to the contrary.
It is a great danger for the modern exegete to read their world back into his sources. I don't think there can be much doubt that Earl has done so here, confusing the modern "Gospel" (capitalized even!) with Paul's good news. That Paul's gospel here has no room for a "preaching Jesus" should come as no great surprise, since his gospel has nothing to do with what Jesus preached. Doherty would have done well to have read Barrett's suggested reason for Paul's epistle while he had the book open, because even if one doesn't find it wholly persuasive, it gives a perspective that is often missed, and doubtlessly missed by Earl.
Put most simply, in Barrett's (and many, probably even most) suggested motivations for the epistle leave little room for Doherty's expectations. The argument from silence might work. This argument doesn't work here, unless Doherty knows an awful lot he's not telling, in which case he should probably tell us. Even if Doherty happens to be right, so far as Romans goes, he gets the right answer for entirely wrong reasons.
It's symptomatic of a large problem throughout Earl's book; a tendency to think things are self-evidently true, when evidence in fact states the contrary. We can find the same in his treatment of middle-Platonism, in his treatment of ancient myth, and so on. He cites sources that present the contrary (and, for the most part, and at least IMO correct) reading, but makes no effort to engage that reading. It ultimately creates the impression that he checks through commentaries for whatever verse he's struggling with, finds the reading he needs, and then runs with it, without bothering to examine the broader picture.
Somewhat ironically Barrett himself often preferred to translate with the more literal "good news" to avoid precisely the mistake Earl has made (Romans, p19). If he'd read the man through, one must wonder why he's not aware of the difficulty. Indeed, it seems we are left a conundrum where Doherty either didn't read Barrett carefully, or didn't take Barrett seriously since he implicitly declares it self-evident that Barrett is wrong without further discussion. Either event reflects poor judgment on Earl's part, and an overconfidence in what he sees as obvious that deters him from further investigation.