If you think you’re big enough to talk s*** about someone you don’t even really know, you should be big enough to deal with the consequences of your actions.
That doesn’t mean you and your sixteen friends gang together when the bullied victim decides to fight back for once, it means either fighting back yourself and winning or taking the beating. At that point it’s your own personal responsibility to follow through, because they won’t care if you’re ready or not when you push that final button.
That’s a lesson one bully learned the hard way when she kept insulting a girl about her pigtails; the girl was apparently at the limit of crap she was willing and able to take that day and finally decided to throw down. The bully was confident in her ability to beat her victim senseless, but that confidence was quickly lost when the other girl came out pulling hair and swinging hard!