Everyone is a hacker. When emotions are at their greatest, you begin to hack.
You may be hacking now, you may have hacked in the past, you may be hacking in the future.
Also, it is very wrong to think that hacking is relative only to computer security.
Bankers, Traders, Politician, Lawyers, Accountants etc etc, are all bound to hack within the context of their sphere of influence and field, when push comes to shove. Whether they be giving an honest employee a bum reference or helping themselves to additional expenses.
It is all hacking because the cognitive processes involved are effectively contriving to subvert the intended process in some way. Whether you call this ethical, fraud or criminality, it matters not.
Also, your ethical boundary may not match with your targets ethical boundary, so unless you establish the ethical constraints with the target before the hack, how can anything be called ethical?
Ethical hacking is two way handshake, whether anyone likes it or not.
What suits you Sir, suits me!
If clients wanted unethical hacking to harden their security they need to say so first.