"naughty words" are not synonymous with "rudeness". You can easily convey a message of contempt for the recipient with flowery, polite words, just as you can easily convey a message of fraternal love with rough words.

If someone told me to mind my language over a casual board game, I'd tell them to fuck off. A friendly jibe is just a friendly jibe, regardless of whether it had the word 'shit' in it or not. Words matter, but far less than intent does - and the intent of telling someone to clean up their act in a casual setting is that they're patronising you.