[bscphil]

As an American, I would not have tipped in that situation. I wouldn't have even considered it. I don't think that's far out of the norm for a situation involving extremely poor service and abusive behavior. I could be wrong but I don't think "Americanism" is the explanation for what happened here, though I agree that our approach to tipping is a bit bonkers overall.

[bombcar]

The "small tip" is to let them know "I didn't forget to tip, I'm tipping you a tiny amount so you know I'm mad".

[bscphil]

I guess that works in theory, but Americans don't generally "forget" to tip. Every time you sign a receipt there's an explicit line for a tip. Apps like Uber have a button you have to press to not leave a tip.