"You will rue the day that your employer lost business because some "user" was prevented from doing her job by your deliberate action."
You might rue it a damn sight more if some numpty introduces something onto the system which then causes an security breach.
In such as case as has been discussed the person doing unauthorised modifications to the company property has most likely broken terms of either their employment or the acceptable use policy. So any IT person defending the integrity of the company's data and systems is doing their job, the user is not by monkeying around with things that do not concern them, are not in their job specs or have the knowledge to do without great risk.
Personally I got no satisfaction from keeping the users in line but did from knowing that I may have stopped some disaster happening.
OK, maybe I did enjoy cracking the whip a little, but only if the user was really stroppy and determined that their way was best and damn company policy.