Bonds and Clemens are just as "guilty" of PED use as Papi, but neither are in because they were unpopular (and terrible terrible people) and regularly didn't want to talk to the media, unlike Papi who was always happy to talk to them and give them quotes/soundbites. The problem with Hall of Fame voting is that, as usual, some of the individual BBWAA members made it about them instead of about the sport.
The thing about ARod is that he didn’t fail a test outside of the 2003 test, either. His punishment was the result of a witch hunt orchestrated by Selig, who wanted to find a high profile player to make an example of. ARod's punishment was a flagrant violation of the JDA.
He never had an official positive test, so he never followed the standard suspension pattern, which at the time started at 50 games. Instead, he was slapped with a 211 game suspension because Selig personally hated ARod and wanted to help do the Yankees a favor and help them avoid paying ARod his huge contract for that year. Michael Weiner also rolled over on the suspension and didn't back his own union constituent.
The whole Biogenesis thing surrounding ARod was such a huge sham:
- MLB's senior vice president for investigations, Dan Mullin, seduced a Biogenesis nurse for information on ARod
- MLB purchased Biogenesis documents that were known to be stolen; Florida investigators warned MLB to stay away from them. In purchasing those stolen documents, MLB committed obstruction of justice and and caused the Florida and federal investigations against Bosch and his clinic to fall apart
- MLB spent hundreds of thousands of dollars to purchase additional evidence, which anyone can tell you isn't exactly a reputable way of doing business
- MLB was blackmailing Anthony Bosch; they ensured his cooperation by saying they'd hand over everything they have to the feds, and stop paying his legal bills, if he didn't say what he did about ARod