Some assorted thoughts here:
-We do not actually know anything about the specifics behind the firing. It could be because he spoke to a podcast at all, it could be because he made remarks that fans reacted negatively to, it could be because Japanese media mistranslated his comments and it blew up over there. We do not -- and are never going to -- know the whole story.
-Firing someone for breaching their contract and breaking an NDA is absolutely standard practice at most companies, and understandably so. In fact, particularly nasty companies will outright sue for that sort of thing. PR departments exist solely for the purpose of managing the brand, and going off-script on unauthorized interviews harms that brand. Even Chris Pranger himself admits that he made a mistake and his current situation is his fault and his fault alone, so Cliffy B is completely out of order.
-That said, it would not be out of the bounds of reason to have let him off with a lesser punishment. Probation, suspension, pay-docking, etc would be equally appropriate. Based solely off the podcast, none of his comments were anything that are going to cause any genuine lasting quantifiable harm to the company, and in the grand scheme of things there is not one customer who will be lost as a result. Consequently, firing him strikes me as slightly heavy-handed, even if Nintendo are completely and entirely within their legal and ethical rights to do so.
-Getting emotional and posting the Facebook message to his family and friends explaining his situation (and mostly beating himself up over what he did) and not switching his settings to private was 100% a bad move that is probably going to make it tougher for him to ever get future employment in the industry -- hence why the post was quickly deleted. It is a pretty sad situation all around.
-Honestly, If Cliffy B really sympathized with Pranger (and his family's) situation, he would not be drawing yet more negative attention to this fiasco as an excuse to badmouth Nintendo.
-People who cheer when individuals lose their jobs and have their lives ruined are definitely taking this whole videogame hobby way too seriously.