Well you can also argue that all the Christians they have been killing have been doing no harm to other religions and are only following their own religion. But even then a lot of Christians have been murdered irrespective of them being a child or an adult.
Why is there any need to make an argument??
If Christians did the same thing in the past, does that mean this is justified?
Why is it that whenever there are attacks by Islamic groups, there are people defending their deeds by saying Christians did this this in the past? Why is this the only counter argument? Why can't they just say that this is wrong?
Two wrongs don't make a right.
Sorry if you misunderstood me. I mean an argument against the ISIS as well. I never said Christians did anything in the past. I meant that ISIS should not have a problem when some other person is following their own religion.