Originally Posted by SamOF

That's fine at Starbucks, but government has to have much stricter guidelines than that on how to use discretion. It's not intended to be a cudgel to punish people who are insufficiently solicitous of a CBP agent (or, in practice, insufficiently white, insufficiently professional-looking, or insufficiently hot). Discretion in this context is actually intended as a way to maintain reasonable continuity between agents and cases—note that prosecutors discuss discretion by using phrases like "no reasonable prosecutor would do x,y, or z." Halfway decent agencies* would have flowcharts, lists of criteria, or precedent-based manuals for agents to use when deciding how to use their discretion. "She was rude to me so full fine is in order" should be a fireable offense.

And I hope, if you think it through, that you actually wouldn't want to live in a country where your perceived level of politeness to a government agent actually materially influences the outcome of your interaction with the government. In practice, of course it happens. But don't cheer it on.

*No idea if CBP counts here.