The US Government has national defense responsibilities. Providing such exploit information to Chinese companies, many with strong ties to the PLA and other government organs, without notifying your own government first, seems irresponsible.
Edit: The only reasonable path seems to inform every government simultaneously, at the same time as the public. How could the EU possibly let Intel sell CPUs, and let Intel inform other governments of vulnerabilities first? So that the other governments have a time window to play with the vulnerability against the EU?
There is a very practical morality at play here. The Chinese government runs protesters over with tanks, imprisons people without cause, attacks their neighbors without cause, etc. Would it be a good thing to aid such a government?
Putting all governments on the same moral plane is counterproductive and nonsensical. Not providing important information to your own government so that they can secure the very systems that protect you - that doesn't seem very practical.
Oh come on, you're making it too easy!
Just as the US would blacklist intel if they told another nation directly first. (this is even true if they told allied nations) we have seen that just being allies does not stop the US spying (and I'm sure does not stop the opposite as well just turns out the others might be better at keeping things hush hush)
Therefore the patriotic and responsible thing would be to help vendors patch their stuff before directly disclosing the bug to any party that would be likely to abuse the exploit.
The NSA doesn't play ball and responsibly disclose exploits to vendors immediately after discovering and profiling them, expressly because they want to use the exploits, so why should vendors be obligated to do the reverse?