Could you give me the URL to this, either publicly or via PM?
Basically if he's enabled embedding, then he's giving permission for people to embed it. Don't want people to embed it? Don't allow embedding. If he wants to control his video performances, he should host them himself.
If the video was recorded by someone else and he wants to put a stop to it, he can file a claim with youtube and they will remove it. He shouldn't be going after the people who embed it, it's not their problem. And if he does, he should be explaining to them why he's (hopefully) politely requesting they remove the embedded video. But IMO there's no legal issue for you - only possibly the person who filmed the video.
And moving onto that, generally speaking in the UK, you should get a signed release from anyone you film. However, I 'suspect' that a public street performer may be giving you an implied right to film them, especially as they can see you filming them and did not stop you. But that's not something I have any specific knowledge of and you'd need to check.
But as you did not film them and you are just embedding youtube code from someone else's youtube channel, there is nothing the original performer or anyone else can do to stop you embedding it. If he feels he has a copyright claim with someone on youtube he needs to file notice with youtube directly. If he feels he has legal issue with you, he should tell you exactly what that legal issue is. And if he does, please do post it up.