User blog comment:B214/High School DxD EX/@comment-98.227.238.52-20150628024801/@comment-98.227.238.52-20150628025321

I think it is more like the kids are chasing after someone and they have been doing so for a long time. So it might not be that they hate Issei by calling him naïve. It is just that they know that this enemy is to dangerous to be captured and imprisoned. So they need to kill them.

And maybe they are trying to protect their future parents from someone who wants to kill them.