The Bro Code Rule 1

Alright, so I recently have taken a break/temporarily broken up with my SO. I'm good friends with his friends, we still hang out and all talk a lot, nothings really changed in our social life, all good. But now at least 2 of our friends (all males), have flirted with me, insinuated some things in conversation, and started talking to me much more. I told my ex SO all of this, and he was unphased. I thought that was CRAZY... I thought he should be mad and that this was a super unloyal/gross thing for them to do! I would be furious if my female friends ever pulled that!! He says it doesn't matter. WHAT DO YOU GUYS THINK?