That's interesting. I'd prefer not to rely on secret evidence, if it's important enough to change your vote it should be important enough to write an article about, as a journalist. Like McGwire's andro bottle. Then the guy has an opportunity to get his side of the story out there (I only tried it once! It was B12! or it's perfectly legal and allowed and here's why...) and everyone can then decide what they want to believe.
Of course if you (as the writer) never publicized it I suppose you could just not vote for the guy and not give out your reasons. The HOFer who deserves to be unanimous is so rare that any voter can pretty plausibly decline to vote for anybody without too much questioning about it.
Nope. That's not a credible reason to withhold a vote, IMO. It's public knowledge or it isn't. Specifically to the example you give, that writer has no idea what's in the vials or if any of the contents ever made it into any player. Could be insulin. Could be B12. Could be morphine. Could be legal, could be illegal. That's not information credible enough to be worthy of excluding someone from the HoF, IMO.
I appreciate the thoughtful replies. It was just something that popped into my head. The story I referenced was eventually written about, but the player wasn't called out by name. I like the pragmatic, benefit of the doubt reply about what could have been in the viles. In this case, the viles were PEDs.