You did, but you didnt. you made a temporary solution. If the person you defended is an "easy" or repetitive target, then they'll be attacked again, and you wont be there to protect them. Then the bullies will take their aggression out on the kid for the humiliation you gave them.
Personally, I would have done the same thing. and after gaining something of a bad reputation for fighting when i gave advice in other threads, I have to say you handled it well. You didnt think, you just acted, whihc is good. Yes, you should try to use your words, but sometimes (like this) you just dont have that opportunity. only if it was me, and especially if the kid was a friend of mine, it would have been a alot worse phsyically for the people bullying him (we're not exactly all on the same page about how homosexuals should be treated where i live with the minority being they hsould be treated equally, whihc i believe).
You took a step in the right direction though. You showed you wouldnt take your friend being abused. Now your firend has to show that as well. I know, its ahard thing to get over the being bullied mentality, but he has to show now that he wont always need you to defend him. So claps for you:
http://claudelabadie.com/en/wp-content/uploads/2010/06/applause.jpg