Advise on RoT

[Lycanhero]

Hey everyone, first of all i'm fairly new at dming and this is my first campaign and would like some advise on something that happend last session with my players.

Having dmed my group through Hoard of the dragon queen and are now a bit into Rise of tiamat my players got to the second counsil meeting.
Wen they went to the Tomb of Diderius, Varram got killed by the Yuan-ti so according to the book the dwarven king doesn't respond well to that so I rp his reaction.
One of my players goes on by saying that the dwarven king should shut up, that they need the party (which is true) and that dwarves can't do anything on their selves and are good for nothing anyway (mind you this is not in his backstory that he doesn't like dwarves, hell one of the party members is a dwarf.)

A bit stunned what to do I thought "I could let the dwarven king get mad and leave the counsil but this would affect the whole party and not just the one player" so I decided against it.
So I let it slide for now and have the dwarf respond that the party needed the dwarves as much as they needed the party.
I have had some reactions of the other players that they didn't like the other player's reaction.

My question is what is your guys opinion and how could I have handeld this better?

[Droodicus]

I would've asked if they were sure. Then if they continued I'd let the dice fall where they may. E.g, the dwarf king leaves and they have veeeeeeeery little chance of making it right

[Zhorn]

Dwarves a good at holding grudges, but they are also driven greatly by honor.
They could still make it plain that they don't look favourably on a certain player, BUT they would be honor bound to do right by the needs of their clan and kinsmen. Tiamat coming to the material plane is a serious dwarf problem (a problem for other races, but dwarves think in terms of dwarves first and foremost).
Swear a blood oath, proclaim that the player will be made to pay for their disrespect, but then get on with what needs doing. Dwarven memories are far reaching, and they can worry about settling any scores at a later date.