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A nasty spat has erupted between Washington and Beijing over the Obama administration's arms sales to Taiwan. As soon as the US made the official announcement of the US$6.4 billion package last Friday, Beijing responded with both harsh words and retaliatory measures. Deputy Foreign Minister He Yafei called in US Ambassador Jon Huntsman for a dressing down. Beijing also suspended scheduled military exchange programs and threatened to impose sanctions against any American company involved in the production or distribution of weapons destined for Taiwan.

The conventional wisdom in the United States is that this episode is no big deal. Those who take a relaxed view contend that China's reaction is in line with its response to previous arms sales. The new brouhaha, the reasoning...