This may have been already stated but two words sums it up easily = Officer discretion.
Let the flaming begin! LOL
Why would there be flaming? The guy doesn't have a problem with getting a ticket. He has a problem being told he wasn't going to get one and then the guy gives him one.
IMO but is a kind of a dick thing to do. Personally for me it's a matter of personal integrity. If you don't like it, don't tell people you are going to or not going to do something.