Regulus had chosen the polite way to make a statement at the wedding, because it was Remus' son getting married, but this wasn't a wedding and this was Slytherin territory. More than that, this was about Society, a place where that tramp with no manners had no place to be in, and he could have all the fun he wanted.
"Since your mental abilities are extremely limited and your manners are even more decimal, let me explain to you what everyone in this room knows already," he said pleasantly. "Draco and Astoria invited you because they have manners. Said manners dictated that you and your husband declined the invitation, because no one wants you here. In fact, the fact that you came is an insult. Again, I understand that you cannot possibly comprehend such basic rules of behaviour since you were raised in some sort of barn. I would suggest a book or ten before you show your face here again. At least if you want your husband to have a place in his family. Then again, you might not care about him or his family, proving that the lack of manners is accompanied of a complete disregard of who he is."
He took a sip of his champagne, and then rested on his knee with a controlled movement. "And Mrs. Lupin, don't insult me again. You won't like the consequences."