hm, i do think you are in the wrong but not because you feel embarrassed by how your friend behaved, just bc of how you deal with your friendships.
Obviously "S" wants to hang out with you a lot, he wants to come along when you meet with others and also invites you when he goes out with his friends. I dont really understand why he always wants to come along with you esp. since you seem reluctant to invite him and I personally wouldnt be keen on hanging out with a bunch of people who dont want me there. Do you believe he is oblivious to this or doesnt believe when you tell him so or simply doesnt care?
On the other hand i imagine it to be awful if a close friend of mine would be too embarrassed to let me meet her other friends and i most definitely would take offense to it if my friend seemed to be so dependent on their opinion.
Since you say that your friends dont even know " S" yet still dont like him, just makes them seem a bit judgemental. If my friends would talk this negatively about one of my other friends they dont know, i wouldnt just stand there and listen, i would tell them to shut it and give that person a fair chance.
It seems to me though that you are too scared to say something like this to your secondary school friends because you worry about losing them.
I can understand that certain behaviour might embarrass someone but it seems " S" lacks total self awareness. So you should have had a serious talk with him and told him you consider him your friend and you would love to bring him along but that his drunken antics (and whatever else) disturb you and if he could stop this. Just using your friends as an excuse is cowardly, bc you are disturbed by this behaviour too and you need to own up to this.
But you really need to think about what kind of friend you want to be and you should stand by your friends no matter what anyone else says. If you were aware of his behaviour it was a very stupid idea to invite him on xmas eve when it was obvious he would be hammered.
He might have made a better impression on your other friends under different circumstances and you should have introduced them to each other while everyone was sober. And if your secondary school friends are truly your friends they would give him a chance at least. That doesnt mean you would always have to bring him along, just occasionally.
Your friend must have been really hurt if he even talked to his father about it. He probably feels like you are embarrassed by him and that you care more about your other friends although you know him much longer.
I suggest you call him and tell him that you didnt mean to make him feel bad and then you two should meet and have an honest and open talk about it.