You can't be serious OP, we really gotta stop with this escapism or whatever it is. Also stop blaming people from the past. ISIS has murdered tens of thousands of Shia and Sunni Muslims, and Shia people have no interest in that terrorist group thriving in Iraq. It affects economy, tourism, politicians, people, infrastructure, image, etc .... It is literally horrible for them in every way. Assad also doesn't benefit from that terrorist group. That terrorist group affected the opposition's image and standing, and just because Assad may benefit from that, doesn't mean that he is directly or indirectly aiding it in any way.
Now to the ideology of these people. First of all, the mass of them are not educated people. Even majority of their leaders. Yes they have common sense like all humans, and thus they are responsible for their actions and consequences. But, generally speaking, they are pretty dumb people who retreat from logic. So no point in debating with them, you are just talking to a wall that way. These people rely on many other scholars(some not even famous, and definitely not from the MB as you suggest) to base their ideology off of. They also rely heavily upon declaring everyone inferior to them. And misusing tenets of Islam.
All their activity revolves around justifying insurgency, terrorism and killing infidels. They are active on the internet making excuses for their behavior and trying to demonize others while also trying to recruit. So most of their 'diplomacy' is trying to draw up 'evidence' to declare everyone heretics. Go to any Arab news social media page or other political websites, you have these clowns ranting about 'infidels' on every post. Or ranting about how they will conquer so and so or destroy so and so. They are also ranting claiming to be 'Muwahideen' in Arabic, ie the concept of Tawheed, which is belief and reaffirmation of belief in a singular God. They pride this like some special title, and also use it to declare many Muslims as infidels. Even though it is nothing special and is the main pillar in Islam, and every Muslim believes in the Oneness of God. Yet these clowns keep yelling and ranting and declaring everyone as heretics, and also have 'Tazkiyah Alnafs' issue, where they try giving themselves a sense of righteousness a degree higher than everyone else but subscribing to this ideology. Many of this people have delusions of grandeur. It is probably one of the main problems.
And in this day and age, so many people enjoy this kind of way of practicing religion. I don't mean ISIS's ideology, I mean practicing religion just for attention/praise and feeling sense of importance. Even though in their hearts that can be very misguided people. Unfortunately, due to the prevalence of people thinking it makes them a better person if they yell/rant or share posts on FB trying to make themselves appear religious, this terrorist group finds a lot of support from people, not necessarily material support, but ideological support. This group is trying to advertise itself as unique, but it is far from that. They have much more ideological support than other Islamist movements. Which in my opinion anyone that has such massive support in this day and age is corrupt. Righteousness that is actually pure, just and not done for attention is not rewarded by the people living in this world. On contrary it is disliked.
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So this terrorist group believes thinks it is permissible to actively without effect of time kill or 'take on' all the 'infidels'. And no I don't mean militaries of other nations, they literally believe they can collectively murder civilian groups that are deemed 'infidels' and they think that is what Jihad is. So they believe they should kill their men, enslave the women and children. For example as they did with Yazidi's. They think a God who created this whole Universe is simpleton who thinks like they do, and wants humans to just keep killing and fighting for 'Sharia' or 'Caliphate' as if these concepts will bring any change. In Caliphates of the past, with actually Caliphs that are supposed to be some of first 10 people to enter Paradise and are divinely chosen, there was civil war , rape and chaos.
The Muslim world and people overseas, need to make sure the arguments these people make are debunked instantly. Sadly, not enough are doing that. Because of hatred and concept of practicing religion for attention, and delusions of grandeur. When people 'pride' themselves as 'Muwahideen' or 'Salaf', they feel special and think this gives them superiority over others. They also believe it makes them appear righteous among the public, thus they love taking this path. Because it reaps social and sometimes material benefits for them. They are not looking for approval and admiration from God, they are looking for approval and admiration from among the people. Thus as I said, people tolerate their views or encourage them.
If you actually are righteous person in your heart, and have no reason to show that off to people, nor call yourself a follower of the 'Salaf' or rant about Tawheed and Jihad or Quran to give image to public that you are some good dude, you're going to be ignored by everyone society and have no voice to influence affairs. And if you try to, you are going to be called a confused person or heretic or whatever. Thus situation is not going to change, because the good people have no voice. There is always going to be severe corruption in the Middle East and dirty politics. The Western people have surpassed that era, and you guys should learn from them. Instead claiming the West is inferior culturally or whatever else, learn a thing or two from them. Their social state is much better, there is no tolerance for lazy ISIS clown type of thinking nor tolerance for corrupt people who gave righteous face to rule or be dominant among social circles for sake of money/fame/women as they had a revolt against those people long ago.