You guys who fly the aeroplane please take a step back for a moment and consider that some people do not enjoy flying particularly and any unusual distraction that could threaten their well-being will frighten them.
I love flyng and I have a current PPL(A). I have flown on lots of commercial flghts as SLF as well but have never seen the A/C mist as described earlier or shown in the pic. I wouldn't jump up screaming about it but I would consider asking cabin crew what it was in case it was harmful.
I think a little more friendly information from the flight deck as well as those awful automated safety briefings (which no one appears to watch/listen to) could also help to alliviate these sort of problems and calm potentially nervous passengers.