One should learn to ignore the obvious as in:
One of things that I've personally understood about the PRC is her similarity to a cheating wife; she swears to be faithful and promises never to sleep around on you again, getting angry if you should even question her about it, talking about trust, yada yada... that is, until you catch her at it again, the next time.
The reason that so many people don't believe that PRC sports are clean is the same as it was historically with East Germans sports; they cheated and even as you caught them at it, will cheat some more. Why? Because the value of their 'winning' was always considered politically more important and valuable than your having caught them at it. Hence, there is a national philosophy to cheat and then do the Shaggy:
ie. deny, deny, deny...
Hence, instead of celebrating the awesome accomplishments of a 16 year old swimming prodigy, many are pulling out the PRC's dirty laundry from their past infidelities. Trust, indeed is a very fragile thing. IMHO, it would take about 20 years of clean no doping results from their winners to remove the taint that they themselves repeatedly earned during the 90's. If every one of their winners today comes back (in all subsequent tests) clean for this big O, then maybe the perception of their integrity will be better in 2016.
Of course, there are a whole slew of people who are now waiting for the other shoe to drop; ie. the finding of dope evidence a few years from now. To be honest, I'm holding my breath over Phelps too; time will tell. But frankly, this really isn't an anti-China thing; if one really wanted to get a sense of sports or the Olympiad's dirty history, then explore the long record of cheating in the Big O; there is a trail of evidence all the way back to Ancient Greece. Unfortunately, the power in the need to win can and does pull not only participants, but many nations too, over to the dark side.