Well it would appear the evidence does not support this claim. Beef and pork go bad at the same rate.
Online information seems on non-refrigerated meat storage seems to be hard to locate -- objectively, this is not surprising, given that the standards for industrial meat production, distribution, and storage at home are systematically based on refrigeration.
Best I can find on the topic is THIS :
http://www.google.com/search?q=cach...apter.asp?chapterDOI=9781847559821-00001+&
(IF that link works, for which no guarantees sorry)
Reading through the section on spoilage, the meats that are more often mentioned than others as having a particular propensity to specific bacterial infections are poultry and pork.
Some pork-specific information is found here :
http://www.recipetips.com/kitchen-tips/t--159/pork-handling-safety-storage.asp
... among which "
With pork being approximately 30% leaner than it was a few decades ago, it is important not to overcook it if the desired result is to produce a cut of meat that is tender and juicy. In the past it was thought that pork had to be cooked until well done to eliminate the risk of trichinosis. Improved production and processing conditions have mostly eliminated the risk of trichinosis but some risk does remain. We still have to be concerned that the meat is handled and cooked properly to eliminate all risks."
Beyond the science, however, the perception that people have historically had that pork was a particularly unsafe meat cannot be discounted.
It is a matter of general knowledge that many of the semitic peoples held, and even today still hold, that pork is an unclean meat, because of sanitary concerns.
It is clear that properly butchered and refrigerated pork is no more unhealthy than other meats -- nevertheless, it is just as clear that housewives and butchers will spontaneously describe pork as being particularly susceptible to spoilage, and that it needs to be eaten more quickly after purchase than other meats, as well as greater care being taken with its preparation before consumption.
You could, clearly, argue that these more impressionistic arguments are "unscientific", which would be accurate -- but I would have a hard time believing that such arguments have not been routinely encountered by members of the forum, and I would argue that these conceptions are common and widespread, regardless of their scientific validity or lack thereof.
