A reading of many Greater Boston newspapers as well as listening to some of the commentary on radio talk shows leave little doubt that the media is building a campaign to force embattled UMass President William M. Bulger to resign his post as head of the Commonwealth’s sprawling system of higher education. The cozy relationship which existed between Bulger’s fugitive brother, notorious killer Whitey Bulger, and two former FBI agents who also played a role in the “brooming” of the 75 State Street federal and state investigations, is at the heart of the media’s push to oust Bulger. The former Senate president was a principal in the lengthy 75 State Street probes triggered by the Boston Globe’s Spotlight team.