Bonds
I think the focus on steroids is misplaced. Yes, maybe Bonds has taken sterioids and maybe steroids helped. It's certain he's benefited from lots of knowledge about medicine and training that wasn't available to Cobb and Ruth. Maybe steroids are "cheating", sure. But we were just talking about Ty Cobb. Come on!
What is new about Barry is not that he might use steroids. What's new is that he's a very good ballplayer — you could make a case that he's the best ballplayer, ever — who we just don't like. He's the son of another great ballplayer, and we didn't really like Bobby Bonds, either. And we knew that dislike was all about race and racial politics, and it wasn't entirely our fault: Bobby didn't want us to like him. (See also Allen, Dick)
And so, Barry always knew he didn't care if we loved him. And he wasn't going to let it bother him.
Yes, Barry Bonds has played in a hitter's era. So did Ruth, Mays, Williams, and Aaron.
Yes, things are different now. But it's all changing, always. Pitchers in the 1950's or the 1970's burnt out their elbows throwing little league curveballs or in 150-pitch college outings. Tearing a ligament used to be career-ending: now you get Tommy John surgery in high school. I remember when nobody had heard of a rotator cuff.
My sense is that Barry wanted to be adored, and he felt cheated when he wasn't. Bobby grew up with that and wasn't going to buy into that game: he never much cared about those folks in the stands, and they always knew it.