If we wish to keep our own values while trading with China we should not agree to extradition treaty.
However China holds the cards and it may cost us. 
As for their system of justice we need to keep in mind a number of factors namely political, cultural and historical that of course does not say much unless we accept that all societies evolve at their own pace and they evolve to their benefit not ours. There are a great many issues on this planet that offend our sense of justice and human rights. We need to take care of our own injustices. We need to take care of Canada. We need to learn about other societies so we can understand why they do things the way they do. There usually is a reason even if it does not make sense to us.