Sometimes people have to be reminded how you expect them how to behave. That's why businesses have an employee manual. That's why we sometimes ask posters to please cut it out. These actions help remind everyone that yes, sometimes we get emotional and that yes, sometimes we forget the context of where we are.
Reminders are the first and most reasonable step towards the problem escalation process, and if done in a respectful manner then leaves the de-escallation process in the hands of the person who you believe started it. It shows them that you don't immediately think that they are a troll, or are causing problems on purpose, and so you respect their ability to manage themselves. (edit: And people managing themselves is what you want. I want it too.)
Adulting. Sometimes it's hard, but it builds respect and trust.