The boycott of Moscow was a failure.

"Boycotting the Olympics would highlight the brutalities of the Chinese regime".

Anyone who knows about international politics knows that already. Those who don't know don't care. Their grasshopper minds will move on to American Idol or the latest dancing show.

Boycotting the Olympics will move us closer to as new Cold War. Is that what you really want?

The link to the beach volleyball showed what you really think. Juxtaposing trivial pleasures with China's brutality shows that stopping (other people's) pleasure is essential to your campaign.
If people didn't enjoy the Gamed you wouldn't be half as keen to atack them.