It is wrong to compare the SSPX with the CPA. The CPA openly declared themselves in schism, bragging in their written constitution that they owed no allegiance to the Pontiff whatsoever. They even usurped the jurisdictions of legitimately assigned bishops and approved publicly the Chinese government's forced abortion policy.
In contrast, the SSPX simply consecrated to protect the traditional Mass from destruction. It never usurped any bishop's jurisdiction and it has always professed its allegiance to the Pope, praying for him daily in its Masses. At the Rosary recited before Mass on Sunday in my chapel we always pray for the Pope's intentions.
Even to compare the two is ridiculous. But the double standard in the way each is treated is instructive. In fact Rome treats the CPA with far more deference--and the American Church even has amicable relations with the Chinese schismatics, though their schism is real and the SSPX's is not.
The concecrations were only 16 year ago, what Archbishop Lefebvre did will be judged by history, I can understand and show sympathy for what he did, and understand the arguements that it was an emergency situation. That said, Rome finally offered in late 2001 the SSPX what Abp. Lefebvre wanted, a global diocese quasi independent of local dioceses, but because of Pride and Bp. Williamsons minions, this offer was rejected. The ball is now in the court of the SSPX so to speak.
As for why they were excommunicated, I can understand the position Rome took. Can one imagine if Abp. Hunthausen, Abp. Weakland and Bp. Gumbelton decided to concecrate their own Bishops without the approval of the Pope?