Snowden, and Greenwald by extension, are perfect examples of how being right about one thing doesn't make someone right about everything. I also have serious problems with how Snowden chose to whistleblow, though the actual whistleblowing was necessary.
There were a lot of options for non-extradition before Russia. Even the route he took when he fled doesn't make a ton of sense unless he's selling the information to America's security competitors. My guess is he genuinely believed in leaking the information and he got paid to do it by one or more foreign countries.
Well the US made a sovereign country president plane land with a threat they will shoot it down then grabbed out the president of a sovereign country from his plane and searched the plane for Snowden. There are probably 3 countries in the world the US wouldn't do this to: China, Russia and Israel. So no, Snowden didn't have much choice.