Anyone rational who wants a durable solution should read for example
Global Jihad: The Future in the Face of Militant Islam (the Islamism of the so called classical islam is strongly related with that of modern radicals; unpleasant but we have to begin with the truth if we want real solutions)
The Devil We Don't Know: The Dark Side of Revolutions in the Middle East (not really a surprise that in the whole Islamic world it is still religion, islam in this case, which strongly shapes the other parts of culture and not the other way around how it is in the other parts of the globe, the 'Saudis' are only part of the problem)
and he will easily understand why ISIS is indeed a huge threat. And not only that for unfortunately Global Jihad does not end with the end of ISIS (neither is 'being peaceful' a guarantee that sharia, at least part of its dysfunctional requirements applied in practice, won't have a vey bad influence over free societies on long run). There is no easy solution to this problem but one thing is quite clear, platitudes like that that what ISIS do is not islam cannot solve the problem on long run.