The point is that if it's legal in the US the agent will never be extradited. Actually its identity will never be disclosed to the Brazilian authorities. Most likely the US will deny it all.
I think this depends entirely on the Extradition Treaty with said country and what offence has been made. Just because what you are doing is legal in you own country does not mean you are necessarily protected from extradition if you break a law in another.
The US won't extradite them, but that only helps while they stay in US ground. Their vacation choices are far more limited, and visiting Black Hat or the Chaos Communication Congress is out of the question.
So if they hack the Brazilian government, they're punished with poor vacation options? This is proportional?
It's unlikely for foreign governments to identify FBI individuals. Until the recent leaks "nobody" complained about NSA hacks let alone individual NSA agents. What makes you think it will be different when FBI leads the hacks?
I don't think it's a change.
The point is that this is an intentionally misleading title and story. This fake news stuff is out of control.