"That because he released non-ilegal things that Snowden was not a whistle blower? And therefore he should be prosecuted?"
Well ya, that could certainly be argued. When you get a security clearance it is made very clear to you that it is illegal for you to release classified information, under penalty of law. You sign plenty of documents to that effect and so on. So if you do, you should be prosecuted because you broke the law.
Now, the twist in that comes from if you revealed the government was involved in something it shouldn't be. That is what it means to be a "whisteblower" you are "blowing the whistle" on an illegal activity (as a referee blows their whistle on an illegal play in sports). Most people would say in that case you deserve protection from prosecution, because while you agreed to keep information a secret, that is different than keeping information of a crime secret.
Hence why someone can argue that the leaks of information about foreign spying aren't whistleblowing. I mean that is why America has the NSA, CIA, NRO, and so on: To spy on other nations. That is their express purpose and if they aren't doing that, there is little reason to keep them around. So revealing classified details about that isn't whistleblowing, at least not by a normal definition of the term.
Also trying to argue semantics about the journalists releasing information is silly. After all, Snowden is the one who originally got his hands on it, and chose what to give to the journalists. He maintains some responsibility for what they choose to release. If there was things he didn't want out, he shouldn't have given that information over. You can't hand information over to someone, with the intent of them releasing it, and then later say "Well but I didn't want them to release THAT!"
So the grandparent is being quite logical. I'm not saying you have to agree with them, but the point they make is valid.