OMG this other bloke sounds like a prize tit, and he should have been shot at birth!
Yup - your dh needs to understand and accept how hurt you are and apologise profusely and sincerely. Give him time and I'm sure he will.
It sounds like dh really isn't friends with this bloke, but that this bloke happens to be part of the fixtures and fittings within an established social group - so in fairness to your dh, it is difficult to avoid contact without avoiding the group.
However, your dh could have and should have made a point of not going to his party.
Remember, dh is male and therefore flawed , with a tendency to crap judgement. After further reflection my money is on dh realising just how upset you feel by this and really trying to make amends. I hope so.......
Take care...