I agree that there are many professional athletes who cheat and truthfully we as a society embrace most of them. Take Lance Armstrong for example, this guy was pumping custom roids and enhancers left and right and no one seems to come down on him for it, hell how many races did he win being artificially enhanced? The thing about it is, he's a likeable guy and we want him to win and succeed.
With Barry it's the opposite, he's truculent, racist, a bad teammate, possible woman abuser, envious and an all around bad guy and these are the reasons people hate him, not because he cheats. Truth be told, so many ball players take them these days its makes it less of an advantage.
I was listening to one of the chemist who used to work at Balco on the radio a few months back and according to him, the custom drugs they use are light years ahead of the tests and it's extremely hard to design new tests to test for the drugs. Also, not being able to do blood tests makes it much harder.