I think slim has an interesting point that is worthy of some discussion. For many of us, books like those from Jonsson, Penton, Franz, and others are the very sources that presented the evidence and questions that become confronted in a JC, or in our decision-making process of leaving the WTS. But the answer to slim's question is quite obvious...it would otherwise be impossible to introduce the matter for discussion, and the social dynamic set up by the Watchtower Society is one that severely penalizes complete openness in this regard. In a setting in which dissenters or questioners are disempowered from freely controlling their discourse, such an ethical "dilemma" (relatively minor IMHO) can only be expected. Without a "white lie" as to sources and one's prior reading habits, the discourse could not even take place unless the dissenter wants to risk facing the reprecusions. The conversation would instantly turn from genuine issues about the WTS and about its teachings (which are worth discussing) to YOU, whether YOU have been obeying the Society's "counsel" on reading literature critical about the Society.
I think slim has a fair question because I've faced it myself on my way out (back in 1990 or so). I had lots of printouts and xeroxes of old Watchtower literature and what not, evidence of doctrinal vacillations, and other things that have bothered me. Of course, I knew I would be asked "Where did you get this stuff?" So I thought I could maybe reply, "I got it from the Internet." Now, you must understand that in 1989 and 1990, the internet was not this big boogeyman it is today. Back then, it was thought of as strictly educational (a resource of information, just like you can get medical info on Medline) and imho a "safe" source I could mention. So I had to ponder that question, because I knew I could not even use this stuff had I not had a "cover" ... otherwise I would've been DF'd in a flash. Fortunately, it never came to that because I was able to leave on my own, fading through successive moves. But what finally convinced me that the WTS was not "God's organization" was not just the stuff I found already prepared in Jonsson, Penton, et al., but what I observed myself and what I researched myself. It was my own original research on the evidence of crucifixion and the early church fathers (such that the Trinity broshure insulted my intelligence when it came out) that I realized for good that the Society was not intellectually honest and "truthful". And I think almost anyone, if they invest the time in doing so, can similarly research almost any issue and come to similar conclusions as those prepackaged in "apostate" books.... especially now since so much info -- in fact, actual Watchtower publications from the past -- freely available on the internet (tho, ironically, now you can no longer cite the "Internet" as a source). So I understand why some questioners want to purchase their own copies of old publications on eBay and other sources (in my day, there was Bethel Antiquarian books), in order to be able to introduce things into discussion.
It is also worth pointing out that the Society itself has been less than up front about its use of "apostate" sources, in particular, the thesis by Jonsson. I have done a discourse analysis of the Appendix to the Kingdom Come book, and it is very easy to demonstrate the intertextuality between the two works, and the Society's own use of Jonsson in their response (including some verbatim parallels in wording). But instead of identifying Jonsson as a source, they systematically merge him with "safe" secular historians and scholars. This erasure of Jonsson as a source is motivated by the same social constraint that dissenters find themselves restrained by....i.e. the Watchtower characterization of "apostate" sources as "poison" and their use as a potentially disfellowshipable offense.
