Anyway, the Cliff's Notes version:

1. I think popular conception of the effect that steroids have on baseball players is fantastically overblown. Show me anything other than anecdotal evidence that they change anyone's game dramatically and we'll talk.
2. Pre-1999, Bonds was one of the ten or fifteen greatest players in the history of the game. Is it really so hard to believe that a man with that kind of talent -- along with a ruthless baseball intelligence and access to improvements in sports medicine that Ruth and Williams and DiMaggio and Mays never could have imagined -- would be capable of refining and upgrading his game as he gets older?
3. This is probably a minority opinion among Giants fans, but I personally don't see much difference between PEDs and weight training, eyeglasses and eye surgery, use of videotape, etc. And insofar as it's cheating, I don't see much difference between the use of PEDs and bat-corking, spitballs, phantom tags, and pretending you've caught a ball that in fact you trapped.
4. Barry's mastery of the game blows away any other player I've ever seen. Until he starts kicking children or molesting dogs or something, whatever moral disapproval his behavior and personality may cause me to feel is going to be utterly trumped by the fact that watching the man play baseball is just a joy.
   

Look, I don't know the actual amount of homers Barry would have hit if he didn't take steroids.  It's speculative and I'll admit that.  Furthermore, who knows whether the steroids made him more injury prone than he would otherwise have been and maybe cost him to lose some HRs during certain periods (or maybe it made him less so -- I don't know).  But it seems like common sense that taking a chemical which makes you stronger so you can swing the bat harder would allow you to put up a lot more HRs.  I mean, if you could increase your bat speed just a little so your fly balls go an extra 5-10 feet, that makes for a lot more HRs over the course of a season.  Considering Barry's involvement with BALCO starting around 2000 and the huge boost in his SLG beginning in 1999 and for the next several years after that, and looking at the number of player-seasons with 60+ HRs all compressed into a few years when it seems baseball had a major steroid problem (when nobody had touched 60 for 40 years before that), I'd say it's pretty hard to doubt the power of those chemicals.