The truth is you can't force anyone to play in a manner you think is appropriate. "This is unacceptable" is actually an unacceptable way to think about something like this. It's unacceptable because you don't have control over them. You would like to, but you don't.

I've encountered plenty of players that I perceive as "bad", we all have, and the unfortunate truth is they are here to stay. You may try and educate them, but in some instances you may come off as trying to harass these individuals. OP could've handled the conversation better, this is a fact, but in the end there is no guarantee the other side won't try to defend "their way", even if it's horrendously awful.