This is not a new rule but rather codifies the existing informal guidelines for posting in MPSIMS.
MPSIMS threads are often started to call attention to current events, including breaking news stories. Many posters value these threads because they offer new information and multiple cites about the event in one place. Often the information is rapidly changing and these threads can move fast. One of the advantages of the SDMB is that with many posters from around the world we often have a poster local to the situation or even involved who can give unique insights.
Unfortunately, since these types of threads commonly involve hot-button issues, they often fall prey to hijacks and rants about political, religious or other emotionally charged subjects. MPSIMS is not the place for such comments, which detract from the usefulness of breaking-news threads. If you wish to use a current event as a springboard for a comment or argument about a hot-button issue, please post it in Great Debates or the Pit. You may post a link to your GD or Pit post in MPSIMS, but do not use that as an excuse to rehash your argument.
To be clear, the rule against political/religious jabs and diatribes applies to ALL threads in MPSIMS, not just those about breaking news. Current events threads are cited because they are where hijacks and rants are especially annoying. All posters are reminded to be considerate of other users and continue to observe this rule. Any violation will be strictly moderated.