If you read the report, the waitress thought it was both rude and comical, which I can only assume she doesn't take her hospitality services seriously. She needs more training to keep her job or find another one that best suits her.
On the other hand, the argument on the table was tipping. American culture says to tip, but when did we shift into tipping becoming a tax added to a bill? A tip is a tip of gratitude for bringing the soda, on time, as ordered, with a cheerful attitude. Not, "here's your Coke, you want anything else? Also, hereâs your [18% tax AND you can also add a tip to that] billâ. --"Here's you're coke sir/maâam (if you aren't already aware of the customerâs name within 1 minute of talking), could I get you anything else to go with that?"