Gain unauthorized access to an account and using it falls under pretty much any standard definition of "black-hat" and in practical terms breaks computer security laws in pretty much all legal jurisdictions which have them.
If you steal a loaf of bread to feed your family it's still a crime.
Regardless of whether or not you think what he did was justified it's still illegal. And there's very few serious crimes for which "publicity stunt" will generally be regarded as a good reason.
Gain unauthorized access to an account and using it falls under pretty much any standard definition of "black-hat" and in practical terms breaks computer security laws in pretty much all legal jurisdictions which have them.