Was this the right thing to do?

My little brother just started middle school (I'm a high schooler). He's impulsive and he HAD to get on the wrong side of the biggest bully in his school. So in his second week he comes running to me (this was after school) with around 7 bullies on his tail. They stopped when they saw me (I kinda have reputation at their school) my little brother said they were gonna beat him up. I could have stopped them but instead I told my brother if he could pick a fight then he could fight it and then i walked away. It resulted in him being really badly beaten up. Was this wrong? I mean, I never had to go through bullying because I thought before I spoke (plus, I happened to have gone through bone-crunching martial arts training since I was 6). But he's too impulsive. Don't get me wrong I dont hate him I just want him to grow up by himself and not be like the other brats who count on their older brothers or sisters to get them out of trouble.