Call them out, tell them you'll only fight one.
Don't lead the fight (Don't throw wild punches, don't punch first unless you have a great oppertunity)
Go with his pace, then, set your own pace out of nowhere.
Dodge, don't panic, or you'll get hit.
He throws a jab, THINK, throw your body/head, a little to the left, and throw a right hook at his jaw, etc. It's all about setting the pace, and thinking.
If you can't think (which I doubt they'll do) or set the pace, you'll probably get knocked out :|
Or, you can just say "I don't want to fight you". Tell someone, and leave them alone.