Of course it will. The western media feed us a daily dose of Isis beheadings and atrocities, the background uneasiness has already been formed. The real reason the public haven't taken it more to heart so far is because they perceive it to be a problem far away from our shores. The cold, hard realisation will hit home in a big way if a Western airline is hit.
The tactics of Isis thus far have been to focus on the territory they want to control in the Middle East rather than attack the outside world. If this is Isis it marks a radical shift of strategy (very likely a suicidal one in the long term because the entire world will be united against them) that will set the world ablaze.
Just look at how Americans stopped travelling in droves during Gulf War One. The theatre of war was nowhere near Europe but the perceived risk still won out.
Getting back to the original topic this guy doesn't have time to play the long game, it would be different MAYBE if he was 18 years old or so. Telling him he has already spent £90k so what's a little bit more to add to the pile is just about the worst advice anyone could ever give. It's akin to chasing your losses in a Vegas casino, at some point you have to call a halt to it rather than piling debt upon debt. Especially in an industry like this where the ends don't justify the means, especially with it being so fraught and exposed, with airline execs constantly putting downward pressure on salaries.