We use the chat box on the first fairway to establish that kind of thing. It's very easy to tell your opponent, "I believe in putting out on every hole. I don't concede putts and expect none in return. Thank you."
Sometimes, when playing with friends, we'll set rough guidelines while going down the first fairway. Agree to concede anything under 1 foot, putts when someone is obviously out of the hole, etc. If someone has a particular putt they want to hit but they are out of the hole they will tell us to let them hit it and we do.
Communication and being polite right away in a match resolves the issue.