My main assertion is that critical destabilisation of an Arab country caused by such an influx is considerably less likely than negative effects in European societies that are already evident here (and that could get a lot worse still; all the way up to the catastrophic scenarios you illustrate); negative effects that should not be more likely to occur in these Arab countries.
Negative effects are already evident in European societies, yet similar negative effects but worse by an order of magnitude would not be likely in Middle Eastern societies because they "have similar cultures"? Are you getting this stuff from Samuel Huntington or something?

I'm afraid realistic thinking beats diaphanous dialectics every time. Adding national and ethnic animosity, social unrest, and economic deadweight to countries that are already unstable and economically-fragile quite clearly would lead to very rapid regional degeneration if ever actually implemented through mediated population transfers.

For all the problems Europe has had with the refugee influxes, they have only now, after all these years, reached the point of becoming mildly-troubling precisely because European countries have been in such a good position (compared to most of the world) to withstand the experience.