Not being nice is when you have them on the hook for as much as possible. Instantly telling them that you're not a mark actually helps them, in comparison. 

 I understand the logic. Every second I spend fucking with them. They're potentially not scamming somebody else. But at least today I just can't be assed.  

 Yeah, sometimes I use them as an aggression outlet instead of stringing them along. Gotta make them useful somehow.