Sorry but I think YABU OP.
We have Sunday dinner virtually every week.
During the week due to work and having a constantly starving DS I often find myself serving food at different times in the evening so whilst we always try and eat together it's not always possible. It's not great but it's life and I'm realistic about it.
However the Saturday evening meal and Sunday dinner is the one time I'm absolutely a stickler for us all eating together as a family.
Sunday dinner is quite a lot of work to shop and prep for but in addition there is an art to making sure everything is ready at the same time.
In this household everyone gets a 15 min warning and then a 2 min notice to be sat down at the table because I'm about to bring the food out. We all start eating together and stay seated until everyone has finished. That's the rules and if you don't like them - you don't get fed
.
If I've spent best best part of 3 hours of the day cooking the perfect roast dinner I'd be pretty pissed of to watch it sat on a plate going cold for 3 minutes - effectively undoing my hard work/wasting my efforts to serve it optimally.
The laundry wasn't urgent - 30 mins wasn't going to stop it being ready for tomorrow.
You prioritised something you wanted (not needed) to do over the work someone had put in to do something for you which is rude.
The fact you'd been busy all day and he'd "just" cooked is a totally separate issue and perhaps you were being somewhat passive aggressive to being late for dinner to make your point???