Same here (iPhone 4S, iOS 6.0.1), dates are missing:

although other podcasts are shown with release date:

On the other hand, and quite surprinsingly, the podcast is shown correctly in iTunes:

According to https://discussions.apple.com/thread/3120228 the missing release date could be caused by an incorrect pubDate element.
However, Reasonable Doubts' RSS feed correctly formats the pubDate element as described in the RSS specification and RFC 822. But what about the rest of the XML file? A syntax error could prevent an RSS reader from successfully parsing the RSS feed and extracting the date information.
Luckily, the W3C provides at http://validator.w3.org/appc/ a feed validation service, which checks compliance with the RSS specification. And W3C is clear, Reasonable Doubts doesn't validate:

Apparently iOS 5 and iTunes are more tolerant than iOS 6 with some "broken" RSS feeds like the Reasonable Doubts podcast.
(As a side note: I found a podcast which looked perfectly right in iOS 6 although not having the day of the week in pubDate, so that wasn't the culprit, as I first (wrongly) suspected. I also found other podcasts with a missing release date (like here and here). The reason for it in these cases is indeed a non compliant pubDate element.)