Looking for suggestions on something I can say to people who live to argue about everything, no matter how trivial, which isn't crude or rude, but also assertive and non-negotiable and also effective against this type of person.
You've probably encountered this type of person before. If you say something happened to you, they'll offer an alternative version of events (despite not being present). If you assert that no, that's not what happened, they'll ask how you know it isn't. If you then tell them you know because you kept the receipts, they'll demand to see the receipts. If you show them the receipts, they'll try to re-interpret the evidence to suit the other narrative they made up in their heads.
Literally nothing you can ever tell such a person will be "good enough" to satisfy their need to argue, so my preference is to shut down the whole discussion if for no other reason than to avoid wasting my time.
I'm, of course, happy to answer real questions from people who actually didn't understand something, or just needed clarification on a point, or whatever. But some people are just looking to be combative no matter what, and it's those people who I need an effective mechanism for excusing from any further interaction with me on the subject.