He was expelled from USSR and eventually end up in the USA.

He thought too that he will never be able to return.

A better comparison would be if a Google employee fled to China after leaking the news that Google was intercepting emails from other mail providers and hacking into other companies' servers.

(I have no particular opinion about whether Americans should consider Snowden a hero or a traitor.)

How is that in any way relevant? User emails != extensive world wide spying, HK != mainland China