I'm a team leader for a group of people including trainees. Recently, I had a chat with a colleague from another department and he made some jokes about the trainee from my team. The joke is not that rude to escalate to the senior manager as it can be read in many different ways but given his smileys and the way he structured sentences clearly tells me that he is making a fun, also he is known for making fun of others.
I want to take this up with him during the next week and I need to find a way to correctly approach this situation. I want to start by clarifying the statements he made and his intentions, but I clearly miss vocabulary here and need some hints how to structure a conversation and give him implicit understanding that it is not fine to make fun of my teammate.
How would you handle this situation properly?