Last week my team was invited to a shared lunch with another team in the same department, the event was organised by managers to promote shared understanding of certain processes. We are lucky enough to have a small kitchen at our office and member of the other team offered to cook pizzas, both meat and vegetarian. One of my good friends and colleague, Emma, is strict vegetarian.
When the pizzas were cooked I observed the team member remove the meat pizzas from the oven followed by the vegetable pizzas using the same utensil. When I saw what he had done I spoke to him and I said "Excuse me but my colleague Emma is a vegetarian, you've just taken the meat pizza out first and then the vegetarian one so you've cross contaminated the two". He looked at me for a moment then laughed and said 'don't worry - she won't mind'. At the point I said quite loudly "How do you know she won't mind? That not for you to decide". This caused other people in the room to stop talking and look up. Feeling slightly embarrassed I left the room. In the end neither me nor Emma took part in the lunch.
I don't regret challenging him, but in hindsight I'm not sure if I could have done it differently. If he had acknowledged his mistake, I wouldn't have raised my voice but it was his casual dismissal and lack of understanding that irritated me. On Friday I had email from my manager saying that the person concerned had emailed her saying that I was unprofessional and I had embarrassed him in front of his colleagues. I don't expect any formal action to come out of this but now I'm worrying that I was unreasonable.