Snowden broke many rules but people really needed to know how much the government hides from them. I don't see the harm in letting Snowden return, even if he keeps on leaking secrets till the end of time, government policy and the bureaucracy isn't going to change much. People will still be kept in the dark about some things.
Yes, Snowden did the right thing by releasing information. In America, we are supposed to be free. There is way to much information that the government knows about us that we have no idea about. Because of this, we can't be considered free and this goes against the values on which the United States was founded.
The sensitive information that Edward Snowden released publicly exposed abuse of power by many within the United States government. Most people did not realize the extent to which the US government spies and monitors activities of law-abiding citizens. The information he released shows human rights violations of people of every ethnicity.
I don't necessarily have a problem with whistle blowers, but if you are a CIA agent and you copy and leak classified info it could cost someone his or her life. I get that it led to an important debate about digital privacy and espionage, but in some circumstances the safety of the many outweighs some need for privacy. That being said, I don't have a problem with Snowden returning to the US.