Friend brought a guy to a dinner party to introduce to the host as a possible date despite being told not to bring anyone, the host turned him down: 'She said I could've just gone along with it instead of embarrassing him'

If you want to do a blind date kind of deal for your friend, you still need to notify them about the date before the other person appears out of nowhere. 

Blind dates are not something I was ever interested in. I hate the idea of getting together with someone I know nothing more than their name and a picture I saw. I don't trust my friends enough to ever hook me up with anybody. But mostly, I don't like the idea of the blind date, as it seems to be a plan made up by other people to get the two people involved to be in a relationship even if they don't want to be in one. The whole thing about it sounds completely messed up. But who knows, maybe I missed out on something. 

I am the kind of person who has linked friends together, and I'm really good at it. If I make two friends from different friend groups meet to see if they like each other, most chances are that they end up together. I have a whole record to back me up. This has worked out so many times that I have stopped doing it because it was too many people being in relationship that started due to me, and when they go wrong they tend to blame the person that made them meet. It has also caused some problems in different friend groups. But when I was still doing it, I never organized something like what this woman did. I never just appeared with a date for a friend without telling them; that sounds crazy! What I usually did was first talk to them about each other and show them their Instagrams. If they liked what I told them, I would arrange some common ground to meet where they weren't obligated to interact if they didn't want to. It could be my birthday party, a normal friends gathering, or just meeting up somewhere. They always knew that they both were going to be there, but it wasn't an obligation for the two people to end the meeting being together. After that, they usually hit it off and start to arrange a date on their own. If they didn't talk to each other all night, I would just drop it. 

That is how you organize something like this. With care, with options, without forcing anybody into a date they don't want to have. You are doing this because you think your friends could work out as a couple, which is great. But if they aren't interested in it, you just stop. It's a good cause; that's the best part of being good, the moment you turn it into an obligation. There is nothing wrong about presenting two people; the problem is forcing them into a date when they never said they were interested in it or without you asking beforehand. So be mindful about what your friends want, and then it can all work out in a more comfortable way.