Suppose you are a christian and people will hunt you down, beat you up, won't give you work, lock you up and hold you responsible for all things wrong in this world. That would feel as really unfair, right?
The argument people use would be: 'Yeah, catholic priests abused young boys so every christian is potentially a child molester!'
You would not like that, would you? And you would say someting like:'Yeah, well, but you can't hold every christian responsible for what other christians do!'
The response of your attackers would be to hit you even harder and use words like: 'Well, your own holy book states that your God ordered you to kill anyone who believes differently then you do:
'However, in the cities of the nations the Lord your God is giving you as an inheritance, do not leave alive anything that breathes. Completely destroy them—the Hittites, Amorites, Canaanites, Perizzites, Hivites and Jebusites—as the Lord your God has commanded you. Otherwise, they will teach you to follow all the detestable things they do in worshiping their gods, and you will sin against the Lord your God.'
You might argue with: 'That it says so in my Holy Book does not mean I comply!' But the other will argue with: 'You follow your God anywhere, you do as he commands, right?'
-'Well, yes, but...'
Before you can finish the sentence you will get hurt. Seriously. And they will hurt your children too 'because they are raised to hate and kill, just like you!'
So now do you understand why it is wrong to condemn every single muslim for what terrorist organisation IS is doing to innocent civilians, especially young girls?
If you don't there is no more hope for you to ever become a good and true christian.