Yes and so is everything else muslims do. For instance, there is a death penalty for muslims who choose not to live under islamic rule. And the only thing that qualifies as islamic rule, of course, is a state ruled by a caliph. [1] And no, the law does not mention the case that there is no islamic state. So sharia quite literally states all muslims should kill eachother. For some reason this is not happening. So every muslim on the planet today has committed a sin in islam, punishable by death. Or to take another issue. There is not a single mention of a headscarf anywhere in either the quran or the hadith. It says to wear loose fitting clothes, the actual word used compares the clothes to being inside a tent. Now look around, do young muslim girls wear loose fitting clothes ?
I am making a somewhat disingenuous argument, but the point is that your argument is disingenuous as well, and for the same reason : when comparing reality with a set of laws, reality is found lacking. This goes for ISIS and for every other law, principle, design, guideline, ... on our little blue ball in the dark.
So your argument is wrong. Of course they don't follow islam perfectly, nobody does and everybody knows. The real reason is "goes without saying", of course, means that you're merely pointing out that there is massive social pressure on this board, and in this country, to agree with that assessment. That I am a racist if I think otherwise. But this is a bullshit argument. It is true, because it would be a socially very, VERY uncomfortable situation if it wasn't true ... which of course doesn't change the fact that it's utterly wrong.
So in short, it doesn't go without saying at all. How much does it really match the religion's instructions ? I would argue it matches it pretty well. They've got a caliph and are waging war against anyone and everyone else, just like their prophet did. That is the basic problem with islamic terrorism : the terrorists, while not 100% perfectly right about their ideology, have a very good point. Islamic ideology glorifies this war of the prophet against the Roman Empire, and the Jewish and other states bordering it, and describes it as a war that can and should only end with total worldwide victory of the religion.
This is what muslims are teaching their children (I hope we can at least agree on those basic facts). And like every other sane person on this planet, their children don't believe them. I didn't believe my parents when they talked about this sort of shit, and I've had a few talks with my daughter where she made it very clear she doesn't believe me either. But when they get excluded out of our society, hide in their religion for it's the only thing that hasn't completely rejected them yet (keep in mind that islamic marriages are arranged. If you have no money, no amount of good looks or talking can help you). And then these people who look like clerics read to them from the exact same books their parents are telling them to live by ... and those books say to fight and kill and you'll be rewarded. Those are the books their parents talked about when they were toddlers sitting on daddy's knee, when they were happy and provided for. Now they're criminals who failed with nothing to lose ... and these clerics read from those books, and those books say to fight and kill ...
The reason this works is the ideology. And I don't care how uncomfortable that basic piece of information makes anyone. Fighting the people who are already lost is a loser's game. You must prevent, so to speak, toddlers from being raised with those books anywhere nearby.
And given how this is escalating, it is a matter of time until we all agree on that point. The big question is, how many people need to die before we agree ? As I said, I have kids and find this "let's ignore it and pretend it doesn't exist" attitude EXTREMELY unacceptable.
And yes, this will cost me a lot of karma on this board. Fuck social pressure. I hope everyone who lowers the integer next to my name on an internet server feels really good about themselves and the actions they took.
[1] https://themuslimissue.wordpress.com/2015/01/02/hijra-in-rev... talks about this issue