Great Herd FactionFollow

I wanted to stay a friend to the centaurs and have worked to keep away from killing them or getting quests to kill them. I dont care if there is a point to have their fac or not, I want mine on the plus side with them. So... I joined a giant group and while we were waiting on our last member I went afk for about a min. When I came back this ******* group was killing centaurs. I didnt hit them but I still got fac for being in the group. They killed 2 before I got out of the group. Now my question...

Is there any way to repair my centaur faction? It should be fairly simple as I only have the 2 hits, but then again it could be ruined forever /cry Thanks for the help