One can no longer, if one ever could, say that any major area of life where discrimination is practiced is unpolitical. So if there was discrimination and oppression going on in the 2008 China Olympics, then it was perfectly acceptable to express another political opionion and create a boycott of it.
No, I do not think that it is acceptable to boycott the 2008 Olympics in China. I believe that the Olympics are a time for the world to come together for a month without involving politics. The athletes train hard for 4 years to reach the Olympics and should not be denied the right to participate over political issues.