Good luck trying to convice everyone to abandon the Olympic Games. It would be incredibly hypocritical to do that: China isn't the only place where human rights get abused. And in your own way, you'd be abusing the rights of other; some of the smaller countries get very little chance to show themselves on the world stage. Besides, you're still not considering what I said earlier: what if is there is some good in this perceived evil?
Take CFCs for example. We know they pollute and damage the ozone layer, so we banned them. But refrigerators used CFCs because they were cheap and fairly easy to make. To use them in places like Africa, home of some of the world's poorest countries, would improve the quality of life for them. Foodstuffs could be kept fresher, for longer, preventing famine and outbreaks of disease. But no, we banned CFCs because they polluted too much. Africa wouldn't always use CFCs; once they developed enough, they could simply stop using them. We wanted peace of mind that we were doing our part of the environment at te expense of some of the poorest people on earth. How can we expect them to develop when we keep holding them back?
Maybe we were right to stop using CFCs; I wouldn't know, and it's not my place to pass judgement on that here and now. It's a question of whether the good outweighs bad. In the context of the Olympics, China is bad because they're occupying Tibet. It would therefore be good to boycott the Beijing Olympics. So far, so good. But what actual good would the boycott cause? Or, in other words, how would it lessen the evil? The answer is that a boycott does nothing. In some circumstances, it may increase that evil because the boycott is motivated by clearing our consciences rather than actually helping Tibet. Therefore, the good does not counter-act the evil.
The alternative, however, is to participate in the Games. The Olympics are designed to promote properity and unity among the world. Paticipating adds to that; not partipating removes from it. Therefore, there is more good in participating rather than boycotting, even if it does not change the situation in Tibet. It simply keeps the balance between good and evil in a state of equilbrium, whereas boycotting will remove from the good. A boycott is not the answer. Not unless we can organise one that would be wholly removed from our own selfish desires of a clear consience.