It can get even murkier. Would you hire a CIA-trained assassin to be a bodyguard? Would you put a general who led a successful attack in charge of defense? What if they were both convicted of crimes in whatever country they were operating in? There are different legal and ethical issues, to be sure, but in both cases the people learned a certain set of skills regarding offense that could be transferable to defense.
By hackers they seem to mean someone convicted of a computer crime.