There's also a fairness factor to keep in mind when third world countries are polled about their views on current events. Several of the countries with the highest levels of support for ISIS are also on lists such as "least access to electricity" and "least access to the internet"
In Nigeria and Bukino Faso, for example, two of the countries with very high polled favorability for ISIS, electricity is enjoyed by less than 15% of the population. Pakistan is a nation with excessively high polled support for ISIS, and they rank near the bottom worldwide for internet access (18% of the population).
So when asking why these people aren't sufficiently outraged about ISIS beheading videos and other goings on, well the vast majority of people in those countries have never even seen a TV news broadcast let alone seen ISIS beheading videos. Is it fair to demand a level of social consciousness to nations jammed full of people who have basically no media access whatsoever?
There was a "Dont know" option. but, i agree that the issue of internet access is problematic and that's why Buddhists and Christians support of ISIS in these places is less of a concern (Although you can't really compare Nigeria to Burkina Faso). the problem is that Muslims do get some information about ISIS or other Radical terrorists organizations, only they get it through other channels like their Imams in mosques. it doesn't matter which information they'd get access to online, their Imam comes first.
As for you question, i honestly don't know. on one hand, yeah, these people don't know how ISIS behave, on the other hand, these people, as poor as they might be, might actually indirectly fund ISIS through giving zakat to a pro-ISIS mosque, maybe even while knowing the mosque supports ISIS. ignorance can very rarely justify criminality.
As for Hector's question: If after they are being presented with all the facts and information they still support ISIS, i don't see any reason to let any of these set foot on Western soil. if they financially support ISIS, we should take financial measures against them. if they actively support ISIS through other means, like giving shelter to operatives or engaging in their propaganda effort, they should be arrested. if they ever fought for ISIS, they should be put down.
The problem is we don't know who is who and finding out means giving tremendous powers to spying schemes that could be turned against us sometime in the future.