User blog comment:Miskos3/Fairy Tail Chapter 334: Sin and Sacrifice, Review/@comment-203.215.121.116-20130608233519/@comment-7418318-20130609081204

The Dragons never said anything about capturing Sting. Most likely f-Rogue just gave all the Dragons the order to capture his past self, since he had no way of knowing which one would end up facing present Rogue (remember that this timeline is fundamentally different than the one f-Rogues comes from, so he has no fore-knowledge beyong Acnalogia turning up at some point).

And as one of those two Dragons said, breaking a few bones doesn't conflict with their mission. So they can and will fight Rogue. And Sting is free game anyway.