followed with ‘I wasn’t aware is so important to you. I didn’t want to insult you and if you felt so, I apologize. The word fuck is one I use very often, but I’ll try to control myself around you’
Note I didn’t insult the coworker (no fuck you or fuck off), but simply said ‘fuck’ out loud due to a job error.
The correct reply is “I don’t see what the big fucking deal is.” Some motherfuckers will never be happy, so just ignore them and do your own thing.