To think it’s unreasonable for husband to agree to his friend coming round when we’re already having a dinner party.

[Nomad68]

This happened years ago, but got brought up again ( by me) and my husband doubled down saying I’d been ‘a bit off’.
We were in our late 20s, just moved into a house. Christmas Eve and we had 2 friends (a couple)Coming for a meal and staying for Christmas Day.
i’d prepared a meal for 4. Sea bass fillets, so it wasn’t a one pot that could be shared between more people.
My husband’s friend turned up. The table was laid and food about to be served. So obviously I had to delay serving. Turns out this friend had contacted my husband asking if it was okay to come round - he’d said ‘yes’.
DH thinks we should have ‘accommodated’ him.
To me this is so blatantly wrong, but DH thinks we (meaning me) should have been more inviting!

Don’t know about the op but at Christmas time, I am usually drowning in food and would be so easy to whip up one extra plate

They had just moved in so probably not much food.

Oh come on! You know how it is at Christmas especially just moved in to new home and guests over for first Christmas there…. Loads food!

my husband and I would have shared a portion and laughed about it: and then stuffed ourselves with cheese and biscuits

OP, I read a good bit of wisdom the other day:
Hanging on to a resentment with someone, is like taking poison yourself, but expecting the other person to suffer instead!?

P.s. Christmas - you- bah humbug!!

Instead of welcoming friends of family in, just bear a grudge for years after instead why don't ya ???....