I'd actually some some input about boundaries when we have 7/8 guests around a table for dinner and suddenly he's triggered and attacks one of them. He has learned over the years not to attack me, but hasn't quite got the message about others. I know that his triggers around dinner include: not having his voice heard at the family table, anxiety over whether all the dishes match, etc etc. The questions how do I respond or manage it? After his outburst he got up and left the table and went to bed. He knew he was wrong, so he put himself in "time out", I was left with shocked guests.
Since you can be affected by his social behavior it's difficult to separate you from him, but you can't control his behavior and unfortunately that means he has a right to embarrass himself (and sadly his behavior can cause you to feel embarrassed too). Let him blow up and leave the table. Once he leaves quietly address the people he offended. Don't apologize FOR him, but perhaps you could talk about how the blow up made things uncomfortable. I'm learning direct communication is best and taking the subject head on really helps me avoid embarrassment. If the friends are close enough friends, and you trust them, perhaps you can try to explain a little about BPD to them. This is very touchy as you don't want to degrade your H or share too much private info with friends, but if they are going to be a part of your life, then they might want to know what is going on with him.
I've had situations where my H blew up on friends. He eventually talked to the person and they talked it out, but the public humiliation for me was so difficult. I can see how his behavior has ostracized us from others. We no longer get invited to certain events and it's painful.
I am conscious of my social reputation. I've had to go to couple's parties alone. I've been left with having to decide whether to make up a lie or tell an uncomfortable truth. I went with the truth. I just said, "He didn't feel like coming." It took a lot of pressure off me and when they saw my H next he had to answer for his absence.