My boss keeps telling me to ‘calm down’ when I report problems. How do I explain that’s sexist?

The one bugging me now is that any time I express frustration, he’ll tell me to “calm down.” Mind you, I am not shouting or crying or anything dramatic, just expressing my legitimate feelings about a problem I am tasked with solving. A recent example was someone in another department holding up my biggest project, claiming a lack of information despite receiving regular updates from my team. When I expressed frustration in an email about this person’s inattention causing unnecessary delays, he replied, “Calm down.”