You argued that since it was in his nature to kill we shouldn't hold it against him.
No, I said you can't say he committed any crimes because he's not human. We shouldn't hold his nature against him at this point because he's seen the error of his ways (I've killed plenty of dragons who are succumbing to their nature) and has helped us rid the world of an evil. He's not getting a pass on future actions - if he were to act up in the future he'll be dealt with...if the devs allow us.
If there was a river you had to cross and it was full of crocodiles...
Is this talking crocodile in RL or in Skyrim? I wouldn't assume it was a nice crocodile just because it spoke to me - I would weigh other evidence or move along if no other evidence were available. We're talking about Paarthurnax who has a history and is helping us defeat an evil (or greater evil) and is a life form much higher than merely being a speaking reptile.
If you must know Meine Grossmutter told us Kinder the Little Red Riding Hood with the real ending.
Spoiler The wolf's abdomen was cut open as he slept, the grandmother was removed alive, rocks were stitched into his abdomen, and when he awoke thirsty he leaned into a well for a drink, was pushed in by the woodsman, and drowned at the bottom of the well. Everyone else lived happily and emotionally scarred ever after.

Since you're pulling anologies from everywhere: do you go into the "Vampires are teh C00lne$$" threads and accuse them of their grandmas not reading Bram Stoker's Dracula to them?