Supposing that an IS warrior would read this, I’d have to say “Assalamu alykum”.
I have to assume that we both are Muslims.
Why? Because he says “Laa illaaha illa Allah”.

Does that same “warrior”, or you if you feel attracted to their heroic stories, do the same for the thousands of Muslims in that region IS is “conquering”? No! Because if they don’t run they get slaughtered! Non muslims, and that is horrible in itself. But also MUSLIMS! By the thousands! And what is the excuse that IS uses? “They are not good muslims!” – “good” being whatever they think is good…

Then if you think that way, read this and think again:

Usama ibn Zayd killed an [enemy] idolater in battle after the latter had said: “There is no god but Allah” (La ilaha illallah). When news of this reached Allah’s Messenger, he condemned Usama in the strongest terms and he said to him: “How can you kill him after he said La ilaha illallah?” He replied: “But he said it with the sword hanging over his head.” The Prophet — Allah bless and greet him — said again: “How can you kill him after he said La ilaha illallah?” He replied: “O Messenger of Allah, he said it in dissimulation (He didn’t mean it, he just said so to avoid being killed).” The Prophet — Allah bless and greet him — said:

“Did you split his heart open (to see)?”

and he did not cease to reprove him until Usama wished that he had not entered Islam until after he had killed that man, so that he might have been forgiven all his past sins through belief.

Narrated by Bukhari, Muslim, Ahmad, Tayalisi, Abu Dawud, Nasa’i, al-`Adni, Abu `Awana, al-Tahawi, al-Hakim, and Bayhaq

It was logical that Usama thought his enemy was pretending to say Shahada, so that Usama would drop his sword and then the guy could kill him. But what does the Prophet (pbuh) say?

You had no idea! What if he was sincere?
Do you know what is in his heart? You killed a Muslim!!!

Dear brother or sister, do you really want to be like Usama? Knowing how he was reprimanded by the Prophet you say you love? Seeing how deep this Sahaba’s shame and regret were? It would have been better for him to become a shaahid (marter) at the hands of that man than to kill him and be the murderer of a brother in Islam!

I wouldn’t wish that feeling to anyone, not you either. But the choice is yours

Maybe you read about it, or not: Islam scholars all over the world have sent out an Open Letter to ‘Abu Bakr Al-Baghdadi’, as he himself suggested during his first sermon. He invited those who agree with him to help him, and those who don’t agree to guide him, right? Sadly enough from those who oppose him all too many have already been killed. Still, these scholars have drafted for him – and for you too! – a document summing up some really important elements where this so called khaliph and his state are in obvious error. I assume that many people who feelattracted to IS actually have good intentions but feel impressed to easily by the tough language used by the organisation.

When you say you do something
for the sake of Allah, than of course

Then please read the very instructive document
even though it is a bit lengthy.

The time invested in it is a good investment
as what is says, and what you’ll do about it,
will determine your afterlife.
And that is for eternity…