I honestly don't think conspiracy theories are encyclopedical (you will not find them in Britannica, Hispanica, Encarta), and unless clearly identified as such, they violate WP:UNDUE. 
To say that the PSOE backed up the Madrid bombings (which is different from backing the "turmoil", but even that...), even if sourced with a POV reference, is not compliant with the other policies in Wikipedia. "Good faith" has three unavoidable limitations (CITE, OR and NPOV). Remember that what "rings true" or is a "state of mind" based on reports that turned out to be wrong in the end, and cannot be fully verified, cannot be included in Wikipedia. If at all, all sorts of conspiracy theories could be included (and even there I have my reservations) in a very specific article, say 14-M Bombing attacks at Madrid, but not in the general Spain article. 
 It would be similar to including a sentence in the History section of United States saying that the Bush administration was behind the 9/11 attacks, according to some sources. Or, as you know, there are hundreds of conspiracy theories of "Spain" against Catalonia, of which I could find dozens of "sources", some of which, to many people "ring very true", but they are not included in Wikipedia, and probably should not, as you would probably agree.
But I would be more than happy to ask (an) administrator(s) and other users with good-standing for their opinion and/or mediation, if you like.