This is not a double standard! Jews and Christians will be doing it by not balancing the study of Holy Scriptures!
On the other hand, Muslims will do it by studying correctly what is stated in their book.
But of course liberal muslims will say that they are the one who do the balance study of their book. I believe, Mohammed would not agree with them if you study his life and practice.
And the moderate, mainstream Muslims will say that ISIS does it by not balancing their study of the Koran. Do you see the problem here?
For the record, I agree with you over all; I think Mohammed (from my limited reading about him) was a bloodthirsty vicious warlord who invented his religion in order to acquire power for himself. I think Jews and Christians are totally wrong to appeal to Joshua for support for war let alone terrorism.
I'm just trying to say that it seems that the consensus of modern muslims would say (and have said) that ISIS is not genuinely Islamic. Having only a limited knowledge about Islam or what the Koran says I'm content to give them the benefit of the doubt on this topic, particularly since parallels can be made in Christianity with out various unbiblical off shoot groups.