I think you are being naive. The Anglo-Saxon world order, aka "Western" alliance represent a cabal that rule with an undeniable superiority complex. Any countries not part of their inner circle are only tolerated because they obey and toe the line. A successful and independent country like China represents a threat to this simply because it is successful without their permission. There is no other way to explain the esoteric behavior of the leading countries of the Anglo-Saxon world order.
China's space cooperation would only be sought once it represented an opportunity as a target for industrial and scientific espionage. Until then, it is isolated and contained from achieving technological parity. Once China can compete at the highest technological levels, it will be included in multilateral technology exchanges, not for the sake of mankind, etc, etc as you are suggesting but because there is something to gain from China. Otherwise, China will be isolated and contained as it is right now, except in cases where it has already achieved such technological parity.