I think the discomfort with the show is perhaps an illusory burden which resides in the foundational view of there being 1) Believers 2) Skeptics.
There are now two types of show:
1 ) Believers - Alex gushes over how wonderful someone is to go against science and follow their calling (for example,. the past life regression hypnotism interviewee). At no point is the interviewee tested to defend what they are proclaiming; the whole thing is just accepted based on the claims made during the interview. THIS DOES NOT INTEREST ME - I want to follow the data, which is what fascinates me about the show.
2 ) Skeptics - Alex prefaces the show with his own editorial, where he dismisses specific comments made during the interview. We then hear the interview, where the person has clearly not understood what type of questions are going to be asked. Afterwards there is often a "cheap shot" where Alex quotes an email exchange with the embarrased (and annoyed) interviewee, as though thier human foibles are more significant than the ideas and science they promote.
The proponents are not believers and the opponents are not skeptics.
I would contend that this is the source of the apparent discomfort with the show, as an attempt to shoehorn guests into preformed ontological bases, will always create problems, whether one is listening to radio, speaking at a conference, working in science focused organization, or posting in a forum. Just as in science, when one runs into a repeatable conflict between predictive models, examining the assumptions and disclosures underpinning the issue, is the first step - rather than attempting to reinvent the whole discipline.
I do not see the guest categorization this way at all. Since science is first and foremost an action (method) it would be better to categorize people by their action sets and not by 'good/bad' positions regarding a 'good/bad' subject. I see (and of course my view will suffer its own predictive weaknesses as well, but is hopefully helpful :)):
1) Sponsors (A legitimate role player in the scientific method) - Who have followed the data and/or have personally conducted testing; yet suffer the weakness in that they are overcompensating emotionally for a perception or reality of being denied access to the scientific method and the body of science, and
2) Official Critical Spokespersons (has nothing to do with critical peer review nor skepticism) - These are not skeptics, in that they have made official peer conclusions and disseminated opinions on behalf of the body of science (due to position held in such) regarding the specific topic at hand; yet cannot be relied upon to be prepared on the topic nor show much history in having credibly researched the material.
3) THEN - there are skeptics. Ones who do not sponsor, and are actively following the data; yet demonstrate the objectivity of not taking the step of publishing authoritative conclusions when they do not hold a full grasp on the material at hand. And when Alex gets an actual skeptic on the show (and he has from time to time) - I suggest your third category is applicable.
Feeding #2) people questions in advance is disingenuous, runs counter to the whole point of the show, and simply serves to support people who have declared themselves to the community, via publication, to be competent on the subject, sufficient to represent the subject to the body of science. Yet cannot demonstrate such a claim.